SAHAYOG
UGC-DAE CONSORTIUM for SCIENTIFIC RESEARCH
(An autonomous Institution of the University Grants Commission)
———————————————————————————————————————
Vol.19 No.1
UGC-DAE CSR Bulletin
July 2010
Online at www.csr.res.in
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Focusing crystal based neutron diffractometer with sample environment of very low
temperatures and high magnetic fields at Dhruva reactor
The high resolution neutron powder diffractometer installed by the UGC-DAE CSR Mumbai Centre has been in
operation at the Dhruva reactor, Bhabha Atomic Research Centre, Mumbai. The design of this diffractometer is in
tune with the standards available at other major neutron scattering facilities in the world. In order to make the best
use of the available neutron flux, some novel design concepts like the use of doubly focusing, asymmetrically cut
perfect crystal monochromator and open beam geometry have been incorporated which enable the use of smaller
samples. This instrument offers a unique sample environment of very low temperatures and high magnetic fields
using a 7 Tesla cryogen- free superconducting magnet with a VTI having a range of 1.5 K – 320 K in temperature.
In this article, we give a brief description of the design and construction of the powder diffractometer and some
recent results that were obtained using this unique facility in the country.
Design and construction
A neutron powder diffractometer is usually designed based on the scientific requirement, constraints imposed by
the available neutron flux on the resolution and intensity, space and hardware considerations. Several users from
universities voiced a demand for a neutron diffraction beamline with high resolution and special sample
environment for determination of magnetic and chemical crystal structures. Typical science drivers being magnetic
field driven charge order melting and insulator- metal transitions in manganites, and magnetic transitions in low
dimensional magnetic systems, to name a few. Very often, such studies require neutron spectrometers with special
capabilities and the present diffractometer has been designed keeping in mind the requirements for such frontline
research problems.
Focusing monochromators with open beam geometry, which are essentially bent perfect crystals, exploit the
angular correlation between the incident neutrons to achieve focusing at the sample position with the same
momentum transfer [1,2]. Earlier experimental studies have shown that focusing in both horizontal (the dispersion
plane) and the vertical plane can be used to increase the intensity of the monochromatic beam without distorting the
lineshape [3-5]. Since the location of the crystal for the present diffractometer is at a distance of about 8.5 m from
the reactor source, it was decided to adopt an open-beam geometry, without Soller collimators, and use a doubly
focusing monochromator in order to achieve high resolution without too much loss in intensity. Monte Carlo
calculations were used to optimize various beamline parameters
[6] and our calculations showed that by using the above,
substantial increase of intensity and an improved resolution
over a wide angular range could be achieved.
Figure alongside shows a schematic layout of the
diffractometer. The doubly bent perfect Si monochromator
(take-off angle = 900 ) consists of nine asymmetrically cut Si
crystals covering an area 17 cm x 13 cm, which are
mechanically bent in the horizontal plane and stacked over
barrel shaped posts to get a vertical curvature. The
monochromator can be aligned to give incident wavelengths
1.17 Å, 1.48 Å, 1.76 Å and 2.3 Å. The flexibility in the choice
of different wavelengths would enable the determination of a
wide variety of chemical and magnetic structures. The
monochromatized beam is led out through a nose cone
collimator and additional slits. The focused neutron beam at the
sample position was 15 mm x 25 mm in size. The complete diffraction pattern is obtained over four overlapping
banks of three linear 3 He PSDs in each bank, covering an angular range up to 1230 . Data acquisition electronics and
software were developed locally [7]. The raw data acquired from the PSDs is converted into equiangular data, using
simple geometrical considerations and data interpolation routines. Equiangular data from different PSDs is
appropriately combined and displayed on the screen for visualization. The performance of the diffractometer was
tested by measuring diffraction patterns of several standard samples like sintered Al2 O3 , Si, Fe3 O4 , etc. The ?d/d,
which is a measure of the instrument resolution, is about 3 % over a wide angular range, indicating very good
resolution. The focusing geometry also enables use of smaller samples (~0.5 cc).
Sample environment
In order to study frontline research problems in areas of magnetism and phase transitions, special sample
environment of low temperatures and high magnetic fields has been provided at this diffractometer. A cryogen free
superconducting magnet with a variable temperature insert has been installed for use with the diffractometer. This
system provides very low temperatures (down to 1.5 K) and high magnetic fields (up to 7 Tesla). An oscillating
radial collimator to cut off extraneous scattering from walls of cryostats and also to reduce the high background
observed at low scattering angles has also been installed.
Recent results
The diffractometer is now being used extensively by the university community and others to study problems in
frontline research areas and the results obtained using this facility have been published in high- impact journals. A
brief description of some recent results is given below:
(i) Field-dependent neutron diffraction study of multiferroic YMnO3 :
Hexagonal YMnO 3 , a multiferroic material, has been in focus due to the recent discoveries involving magnetism
driven ferroelectricity and new insights into the interplay between electric, magnetic and elastic degrees of freedom.
Giant magnetoelastic coupling recently observed in YMnO 3 gave rise to the debate as to whether the magnetic field
dependence of dielectric constant in this compound is caused by magnetoelectric coupling, which requires an
ordered magnetic state, or due to exchange-striction driven magnetoelastic coupling. To address this question,
magnetic field dependent neutron diffraction measurements were carried out on our diffractometer, which
essentially showed that it is magnetoelasticity that dominates over very weak magnetoelectric coupling in
hexagonal YMnO 3 . Field-dependent neutron diffraction (ND) patterns were taken at several temperatures and some
of the patterns are shown in Fig. 1. The patterns were analyzed using the Rietveld method and various structural
parameters, including Mn-O bond distances and O-Mn-O bond angles in the antiferromagnetic and paramagnetic
states, were calculated (Fig. 2). These were then correlated to the magnetic field dependent dielectric constant. It
was observed that a relatively small field of 5 Tesla is sufficient to bring in significant changes to atomic positions
and hence, to the bond angles and distances, reflecting the dominant role played by magnetoelastic coupling over
that of magnetoelectric coupling [8].
Fig. 1. (a) Rietveld refined ND data taken at
300 K, and (b) at 60 K in 5 T magnetic field
Fig. 2. Temperature and field dependence of structural
parameters of YMnO 3 in zero- field (¦ ) and 5 T (?)
magnetic field; O1, O2 represent apical and O3, O4
represent equatorial oxygen atoms, respectively.
(ii) Evidence for magneto-electric coupling in Ca 3 CoMnO6 :
Ca3 CoMnO 6 is a quasi 1D compound with a spin-chain structure made up of the alternatively placed CoO6 trigonal
prism and MnO 6 octahedra. This low dimensional compound exhibits long range antiferromagnetic ordering around
TN = 15 K, which makes the magnetic studies on this compound more interesting. The low temperature magnetic
structure of Ca3 CoMnO 6 was investigated by neutron diffraction (ND) experiments carried out between 2 K and 30
K, with and without an external magnetic field. ND patterns recorded at zero and in external magnetic field at
selected temperatures below and above TN are shown in Fig. 3. The intensities of the magnetic peaks indexed as
(101) and (110) were tracked as a function of temperature, in H = 0 and 5 T fields. The influence of magnetic field
on these peaks can be clearly seen in Fig. 4. The application of magnetic field reduces the intensity of (1 0 1) peak,
whereas the (1 1 0) peak intensity increases in the presence of magnetic field. For Co ion (6a position and
antiferromagnetically coupled), in zero field, the magnetic moment value increases as the temperature is increased
from 2 K to 5 K. However, on further increase in temperature to 10 K, the moment values decreases. However, for
Mn (6b position and ferromagnetically coupled), the moment decreases with increasing temperature. The external
magnetic field drives the antiferromagnetic Co into a ferromagnetic state above 5 K, thus playing a definitive role
in modifying the spin-structure in Ca3 CoMnO 6 at temperatures below TN. The effects of external magnetic field
have also been clearly observed on the dielectric properties of Ca3 CoMnO 6 . Thus a structure-property correlation
could be established using neutron diffraction studies carried out at low temperatures and with application of
magnetic field in Ca3 CoMnO 6 [9].
Fig. 3. ND patterns at various temperatures with 2
K pattern Rietveld fitted. Inset shows the
emergence of the magnetic peak (dotted vertical
line)
Fig. 4. ND patterns at selected temperatures under
H = 0 and 5 T. Integrated intens ities of (101) and
(110) magnetic reflections with respect to
temperature in 0 and 5 T field are shown at the
bottom
(iii) Neutron diffraction studies on a new diamond-chain compound Ba3 Cu3 Sc4 O12 :
Azurite has the diamond-chain structure, where the system consists of isolated chains of corner-shared diamonds,
and when combined with antiferromagnetic couplings, it results in a highly frustrated system. Neutron diffraction
(ND) measurements were carried out on Ba 3 Cu3 Sc4 O12 , which has a structure slightly different from the above
diamond chain in that the alternate Cu diamonds are perpendicular to each other. ND measurements carried out in
the temperature range 2 K – 300 K. Fig. 5 shows the refined ND pattern at room temperature, signifying that the
compound is in single phase. Measurements below 16 K confirm the existence of antiferromagnetic interactions by
the appearance of a purely magnetic peak at low angles. The magnetic structure found to be compatible with a
magnetic propagation vector k = [0 1 0]. Interestingly, this magnetic peak was found to have suppressed completely
under an external magnetic field of 7 Tesla, clearly indicating that there is a change in the spin arrangement (Fig.
6). This also confirms the existence of competing interactions and the magnetic field helps in selecting a particular
configuration. This study along with other complementary studies carried out on this system confirms that the
magnetic order is complex and is greatly influenced by the external magnetic field [10].
Ba3Cu3Sc4O12
(a) T = 300 K
50 K
2K
2 K, 7 T
λ = 1.48 Å
ICal
a = 11.898 Å
c = 8.390 Å
c/a = 0.705
IObs - ICal
Bragg Peaks
40000
Intensity (a.u.)
Intensity (arb. units)
60000
IObs
20000
0
20
40
60
80
100
120
5
10
15
20
25
30
2 θ (degrees)
35
40
45
Fig. 5. Room temperature Rietveld refined ND Fig. 6. ND patterns of Ba 3 Cu3 Sc4 O12 taken at 50
pattern of Ba3 Cu3 Sc4 O12 taken at Dhruva
K and at 2 K with and without a magnetic field
of 7 Tesla
References
[1] M. Popovici, W.B. Yelon, J. Neutron Res. 5 (1997) 227.
[2] I.Ionita, A.D.Stoica, M. Popovici, N.C.Popa, Nucl. Instr. Meth. A 431 (1999) 509.
[3] M. Popovici, A.D. Stoica, and I. Ionita, J. Appl. Cryst. 20 (1987) 90.
[4] W. Buhrer, Nucl. Instr. Meth. A 338 (1994) 44.
[5] L. Pintschovius, Nucl. Instr. Meth. A 338 (1994) 136.
[6] A.V. Pimpale, B.A. Dasannacharya, V. Siruguri, P.D. Babu and P.S. Goyal, Nucl. Instr. Meth. A 481 (2002) 615.
[7] S.S. Pande, S.P. Borkar, A. Behere, S. Prafulla, V.D. Shrivastava, V.B. Chandratre, P.K. Mukhopadyay, M.D.
Ghodgaonkar, P.S.R. Krishna, S.K. Paranjpe, M. Ramanadham, V. Siruguri and P.S. Goyal, BARC Newsletter 266 (2006) 2.
[8] A.K. Singh, S. Patnaik, S.D. Kaushik and V. Siruguri, Phys. Rev. B81, 184406 (2010).
[9] S.D. Kaushik, S. Rayaprol, J. Saha, N. Mohapatra?, V. Siruguri, P.D. Babu, S. Patnaik, and E.V. Sampathkumaran, J. Appl.
Phys. (in press).
[10] B. Koteswararao, A.V. Mahajan, F. Bert, P. Mendels, J. Chakraborty, V. Singh, I. Dasgupta, S. Rayaprol, V. Siruguri, A.
Hoser and S.D. Kaushik, unpublished.
V. Siruguri, P.D. Babu, A.V. Pimpale, S. Rayprol and S.D. Kaushik
for more details, contact vsiruguri@csr.res.in
Highlights of scientific research in the Surface Physics Laboratory
An important area of our work has been to study embedded systems like rare gas bubbles of nano-meter size
implanted in Al matrix. Rare gas (RG) bubbles in aluminium is an interesting embedded nanosystem, where the
bubble radii have been reported to vary from fraction of a nm to less than 10 nm, depending on implantation
conditions. The repulsive pseudopotential of RG atoms in Al makes bubble formation energetically favourable. It
was established that the binding energy shift observed in rare gas core- levels as well as the change in core-level line
shape manifested through the variation of the Doniach- Šunjic asymmetry for different implantation energies is
related to final state screening of the core-hole by Al conduction electrons. The strength of the screening was
inversely proportional to the radius of the bubbles, and thus the bubble size was also could be ascertained. Bimodal
depth and size distribution of rare gas bubbles was observed in Ne (Phys.
Rev. Lett. 92,115506, 2004; Phys. Rev B, 77, 104119, 2008; ibid 79,
125409, 2009).
Because of their small size and proximity to the Al surface, these
bubbles exhibit quantum confinement and interference. Aluminium bulk,
surface, and multiple plasmons have been observed in the core- level
spectra of rare gas (Ne, Ar, and Xe) nanobubbles in Al, whose intensities
are even higher than those of Al metal (Fig. 1). Both intrinsic and
extrinsic bulk plasmons are detected, but they exhibit diametrically
opposite intensity variation due to change in the size and implantation
depth of the bubbles. The intrinsic plasmon is excited because of the
nanometer size of the bubbles, and its intensity decreases with increasing
bubble size. The extrinsic plasmon contribution increases with
implantation depth. The variation of surface Plasmon intensity with
bubble size and emission angle unambiguously establishes the existence
of the bubble surface plasmon that is most intense in Ne. Furthermore,
the existence of bubble surface plasmon is demonstrated. The generality
of the present work is established by studying three rare gases; however,
interesting differences in their behaviour are also observed. (Phys. Rev.
Lett. 104, 036803, 2010).
Our work on plasmon excitations on Al surface (Phys. Rev. B. 67,
165416, 2003) motivated two very renowned groups in photoelectron
spectroscopy (Prof. M. Šunjic and Prof. S. Tougaard) to perform
theoretical calculations and good agreement with our experimental work
was obtained. In this paper, the line shape of the Al surface and bulk
plasmons were studied as a function of angle of photoelectron emission.
An asymmetric line shape was observed in normal emission, which
becomes more symmetric in grazing emission. Furthermore, the
importance of the interference process in determining the intensity and
line shape of the plasmons was shown.
Metallic adlayers on quasicrystalline single grain substrates like
icosahedral Al-Pd-Mn is another interesting area of our research. Studies
on alkali metal adlayers answered the fundamental question that even
free electron metals would show quasicrystallinity. Using electron
diffraction, it was shown that free-electron metals, such as sodium and
potassium, form a highly regular quasiperiodic monolayer on the fivefold
surface of icosahedral Al-Pd-Mn and that the quasiperiodicity propagates
up to the second layer in sodium (Fig. 2). The photoelectron
spectroscopy results show that the quasicrystalline alkali- metal adlayer
does not exhibit a pseudogap near the Fermi level thought to be
characteristic for the electronic structure of quasicrystalline materials.
Calculations based on density functional theory provide a model
structure for the quasicrystalline alkali- metal monolayer and confirm the
absence of a pseudogap. (Phys. Rev. B 79, 134206, 2009; ibid 73,
054432, 2006).
In last few years, we have extensively studied the material
properties of Ni-Mn-Ga ferromagnetic shape memory alloys. For this
work, the different existing facilities in the institute was used. The
collaborative nature of this work has motivated different researchers
from within and outside the institute to work on this exciting new class of
smart material. Thus, this research activity has not only produced high
quality publications, but it also fruitful collaborations have been built up;
FIG. 1 . Ne 1s, Ar 2p, and Xe 3d core-level spectra
of rare gas nanobubbles in Al (open circles)
compared to the 2s spectrum of aluminium metal.
The fitted curve (black line), the main peak
components (green lines), the bulk plasmons: 1ωp
(blue shading) and 2ω p (blue line), surface plasmon:
1ω s (red thick line), multiple plasmon: 1ω p + 1ωs
(black dot dashes) are shown. The arrows show
1ω p and 1ω s related to Xe 3d3/2. The core-level main
peaks have been normalized to the same height
and aligned to zero loss energy.
Fig. 2: (a) LEED pattern of a clean i-Al-Pd-Mn surface.
Diffraction spots are numbered to facilitate their
identification in the intensity profiles (shown in (d)) along
the dashed line going through different spots. (b) and (c)
show LEED patterns measured at 130 K for different Na
and K coverages on i-Al-Pd-Mn, respectively. Images are
shown in inverted gray scale where black indicates the
highest brightness. (d) Intensity profile as a function Na
coverage along the dashed line is shown in (a). (e) The
atomic structure of an adsorbed K monolayer on the AlPd-Mn substrate where Al: small open circles, Pd: small
gray circles, Mn: small black circles, and K: large gray
circles.
for example, with universities and institutes like Banaras Hindu University (Varanasi), Rajasthan University
(Jaipur), M. L. Sukhadia University (Udaipur), Center for Advanced Technology (Indore), National Metallurgical
Laboratory (Jamshedpur), I.I.Sc. (Bangalore), and S.N. Bose Centre (Kolkata). The work in this area involved high
quality sample preparation, their structural, thermal, transport, galvanomagnetic and electronic structure studies.
The experimental data were supported and understood with the help of state of art density functional theory.
Ni2 MnGa is a ferromagnetic Heusler alloy with large local moments on Mn (3.82 µB). This material is of
immense recent interest because it exhibits highest known magnetic field induced strain of 10% at room
temperature in a moderate magnetic field of about 1 Tesla. This makes it an important candidate for practical
applications, since the response in magnetic- field-driven shape memory alloy is faster and is more efficient than the
conventional SME driven by temperature or stress. The martensitic transition in Ni2 MnGa was first reported by
Webster et al. Ni2 MnGa has an L2 1 structure at room temperature. The structural transition is characterized by the
martensitic start temperature TM= 200 K, in which the parent ferromagnetic cubic (austenitic) phase transforms to
the martensitic phase with modulated orthorhombic structure. The parama gnetic to ferromagnetic Curie transition
occurs at TC= 376 K, which is above TM. In the nonstoichiometric compositions like Ni2+x Mn1- xGa, the martensitic
and magnetic transition temperatures, magnetocrystalline anisotropy, enthalpy, and saturation magnetization are
highly sensitive to the composition. The substitution of Mn with Ni results in the increase of TM and decrease of TC
with increasing x. For the compositions with x greater than 0.2, TM is larger than TC. Depending on composition,
the Ni-Mn-Ga martensitic phases have been reported to assume complicated monoclinic or tetragonal structure with
5M modulation or orthorhombic structure with 7M modulation. The 7M (5M) phase corresponds to seven- layer
(five- layer) modulation of the (110) planes in [1 0] direction in the austenitic phase. From a Rietveld analysis of
the x-ray powder diffraction data, we have shown that Ni2 MnGa in the martensitic phase has a 7M orthorhombic
structure in the Pnnm space group. However, a tetragonal phase that does not exhibit any modulation has been
reported for nonstoichiometric Ni-Mn-Ga with Ga deficiency and Ni and Mn excess. A major disadvantage of
Ni2 MnGa is that it develops cracks and fails to actuate after prolonged use. This brittleness and requirement of good
quality crystals for actuation has resulted in intensive search for alternatives like Mn2 NiGa. Mn2 NiGa is a recently
discovered ferromagnetic SMA in the Ni- Mn-Ga family. It has a high Curie temperature and a martensitic start
temperatures of 588 and 270 K, respectively. Ferromagnetism in Mn2 NiGa is surprising because direct Mn-Mn
interaction normally leads to antiferromagnetic alignment. The geometry of the Fermi surface (FS) is responsible
for a variety of phenomena like spin or charge density waves, Kohn anomalies, Friedel oscillations in metals. If the
FS has parallel planes, strong electronic response can occur at the wave vector that translates one parallel plane of
the FS to the other. This wave vector is called the nesting vector (n.v.). FS nesting has been reported to cause
softening of the transverse-acoustic (TA2) phonon mode along the [110] direction resulting in a modulated
premartensitic phase of SMAs like Ni2 MnGa and Ni-Ti. Recently, an inelastic neutron scattering study on
Ni2 MnGa showed the presence of charge density wave in the martensitic phase resulting from FS nesting. Thus, it
is worthwhile to study the FS of Mn2 NiGa, particularly because the relatively large tetragonal distortion is likely to
modify the Fermi surface.
We have shown using density functional theory and photoemission spectroscopy that the lower-temperature
tetragonal martensitic phase with c/a= 1.25 is more stable compared to the higher-temperature austenitic phase.
Mn2 NiGa is ferrimagnetic in both phases. The calculated valence band spectrum, the optimized lattice constants
and the magnetic moments are in good agreement with our photoemission spectroscopy data. The majority-spin
Fermi surface (FS) expands in the martensitic phase, while the minority-spin FS shrinks. FS nesting indicates
occurrence of phonon softening and modulation in the martensitic phase (Europhys. Lett. 80, 57002, 2007). Total
energy calculations have been performed to arrive at the ground state crystal structure, and magnetic properties and
density of states of Ni2 MnGa are in excellent agreement with experiment. The work showing the existence of large
negative magneto-resistance in different compositions of Ni- Mn-Ga was published in Appl. Phys. Lett. 86, 202508,
2005. Another important aspect of the work is prediction of new ferromagnetic shape memory alloys on the basis
of density functional theory, for example Ga2 MnNi and Mn2 NiIn. Among them, Ga2 MnNi has been prepared and
experimentally studied (Phys. Rev. B 78, 134406, 2008; Appl. Phys. Lett. 94, 161908, 2009).
An unresolved issue in Mn2 NiGa is its crystal structure. It was
reported in literature that its structure to be nonmodulated tetragonal in
the martensitic phase, while for a system exhibiting MFIS, a modulated
structure is expected. Our powder x-ray diffraction studies of Mn2 NiGa
ferromagnetic shape memory alloy shows the existence of a 7M
monoclinic modulated struc ture at room temperature (Fig. 3). The
structure of Mn2 NiGa is found to be highly dependent on residual stress.
For higher stress, the structure is tetragonal at RT, and for intermediate
stress it is 7M monoclinic. However, only when the stress is
considerably relaxed, the structure is cubic, as is expected at RT, since
the martensitic transition temperature is 230 K.
Recently, we have embarked on studying the (001) surface of NiMn-Ga single crystal. The surface study is important because suitable
lattice matched thin films and multilayers can be grown, resulting in
multifunctional properties. The challenge in the surface study of a
multicomponent metallic alloy is to obtain a stoichiometric and
atomically clean surface. To achieve this, we have performed repeated
cycles of sputtering and annealing at higher temperatures. The surface
composition is determined after each cycle by recoding x-ray Fig. 3: Le Bail fitting (solid line) of powder XRD
photoelectron core- level intensities, defined by the area under the least- pattern (black dots) of Mn2NiGa in Fig. 1(b) by (a)
5M+L21, (b) monoclinic 5M+L21, (c)
square fitted peaks of Ni 3p, Mn 3p and Ga 3d. We find that sputtering tetragonal
monoclinic 7M+L21. The residue is shown as a dashed
results in a surface that is rich in Ni and deficient in Mn. However, as
black line. Insets show the data in an expanded scale.
the annealing temperature is increased, Mn segregates to the surface and
at sufficiently high annealing temperature the Mn deficiency caused by sputtering is compensated. A four- fold
LEED pattern is obtained in the austenitic phase for both Ni2 MnGa and Mn2 NiGa (001) surfaces (Surface Science,
603, 1999, 2009).
Last but not the least, important work has been performed in our group in ultra high vacuum
instrumentation, something that is quite unique in Indian scientific scenario. An inverse photoemission
spectrometer with a photon detector comprising of acetone/CaF2 Geiger Mueller type counter and a low energy
electron source was fabricated. The counts were enhanced by a factor of three compared to what was reported
earlier by using higher pressure of acetone. Unlike other gas filled detectors, this detector works in the proportional
region with very small dead time of 4 µs. A detector bandpass of 0.48±0.01 eV full width at half maximum is
obtained (Rev. Sci. Instrum. 76, 066102, 2005). The inverse photoemission spectrometer is now in regular use for
performing experiments to probe the unoccupied states. Besides, a water cooled Knudsen cells that are heart of a
molecular beam epitaxy system have been developed in our laboratory to deposit metals under ultra high vacuum
up to temperatures of 1300 K. The cell provides
excellent vacuum compatibility (10-10 mbar range
during operation), efficient water cooling, uniform
heating, and moderate input power consumption (100 W
at 1000 °C). The thermal properties of the cell have
been determined (Rev. Sci. Instrum. 75, 4467, 2004).
Recently, an ultra high vacuum compatible sample
holder for studying complex metal surfaces that require
sputtering and annealing to high temperatures under
ultrahigh vacuum (10- 1 0 mbar range) for obtaining the
clean, ordered and stoichiometric surface. A resistive
heater is fixed to the sample holder and not to the
sample plate, and thus can be thoroughly degassed
initially to high temperatures without heating the
sample. The heater, which is mounted vertically on the
sample holder frame, slides into the sample plate of Dr. S.R. Barman receiving Materials Research Society of India
rectangular cross-section during sample transfer. For (MRSI) medal (2010)
efficient cooling that is required for adlayer deposition, Cu braids can be pressed on the sample plate from both
sides through a screw mechanism (Rev. Sci. Instrum. 81, 043907, 2010). A significant aspect of our
instrumentation work is that all the equipments fabricated are being used regularly for actual research work of the
group as well as by scientists from other Indian universities and institutes.
S.R. Barman (barman@csr.res.in)
New Instruments
15 Tesla cryogen-free magnet
A 15 Tesla cryogen-free magnet with an inbuilt variable temperature insert (VTI) to vary the sample temperature
from 1.6 K to 300K has been installed at the Kolkata Centre under the aegis of DST, Govt. of India.
Magnetoresistance and Hall voltage measurements up to 15 Tesla field can be done in the said temperature range.
0.5
Resistance(Ohm)
0.4
Nb3Sn
without field
0.3
5 Tesla
10 Tesla
15 Tesla
0.2
0.1
0.0
0
5
10
15
20
25
30
35
40
45
50
55
T (K)
The figure shows resistance vs. temperature plot of a standard Nb3 Sn superconductor in the presence of magnetic
field up to 15T. The superconducting transitions temperature is found to shift towards lower temperature with the
increase of magnetic field as expected.
D. Das (ddas@alpha.iuc.res.in)
Ferroelectric loop (P-E) tracer for ceramics and thin films
60
20
(a)
(b)
P (µC/cm2)
30
P (µC/cm2)
One commercial ferroelectric loop tracer (P-E
loop tracer) supplied by M/s Radiant Instruments,
USA capable of measuring ferroelectric hysteresis
loops, leakage current, fatigue etc., on ceramics
and thin films samples is installed. The following
are the specifications of the system at the Indore
Centre:
0
-30
-60
-300
-200
-100
0
100
200
300
E (kV/cm)
-20
-15.0
-7.5
0.0
7.5
15.0
E (kV/cm)
0.50
(c)
Room temperature P-E loop measured at 50 Hz of
0.25
P (µC/cm2)
Voltage: ± 100V & ± 10 KV (with external
amplifier)
Frequency range: 0.03Hz to 100kHz
Minimum leakage current : 2 pAmp
Test fixtures for measuring at room temperature
and high temperatures available.
0
(a) 300 nm thick PZT standard sample
(b) Polycrystalline BaTiO3 sample
(c) Polycrystalline multiferroic BiFeO3 sample
0.00
-0.25
-0.50
-20
-10
0
10
20
E (kV/cm)
V.Raghavendra Reddy (vrreddy@csr.res.in) and Ajay Gupta (agupta@csr.res.in)
RF-Ion Source
A new RF-ion beam source (which replaces the old DC- ion beam source) has been installed at the Indore Centre in
May 2010. This ion source produces an ion beam of desired gas (Argon, Nitrogen, Oxygen etc.) with a diameter 30
mm at source. This ion beam can be used to sputter a target of choice and subsequently to deposit a thin film. The
ion source uses RF to ignite plasma and a RF electron source to neutralize the ion beam. Therefore both conducting
as well as insulator materials can be sputtered. The stability of ion beam current, voltage is very good making it
possible to prepare multilayers with a very low variation in the individual layer thickness. This source was tested
and optimized for deposition of various types of thin films and multilayers. As an example, x-ray reflectivity
pattern of W/Si multilayers with 20 and 30 bilayers is shown in fig. 2.
Target
Mass Flow
Controller
3
NEUTRALIZER
X-ray reflectivity
10
[W (1.5nm)/Si(3 nm)]20 or 30 Multilayers
10
-1
10
RBragg=68%
RBragg=64%
-3
10
-5
10
30 BL (×100)
20 BL
Fit
-7
10
0.0
0.1
0.2
0.3
-1
qz( Å )
Fig.1: A photograph of the RF-Ion Beam Source installed in a Fig.2: X-ray reflectivity pattern of W/S i
vacuum chamber for thin film deposition using ion beam multilayers prepared using RF-Ion Beam
sputtering.
Sputtering.
Mukul Gupta (mgupta@csr.res.in)
X-ray diffractometer:
A new x-ray diffractometer (Bruker D8 Advance) was installed at
the Indore Centre in June 2010. This diffractometer has a sealed
tube x-ray source giving Cu-Ka x-rays. The standard sample
holder of the diffractometer has a 9 sample changer, making it
possible to measure up to 9 samples in a series. The diffractometer
uses a 1-D position sensitive detector based on silicon drift
detector technique which reduces the measurement time
significantly without reduction in the diffracted intensity. The
maximum global count rate handled by this detector is ~ 108 cps.
Both thin film and powder (or pellet) samples can be analysed
using this machine. The inset in the photograph of the XRD system
is the sample holder. As examples, the XRD patterns of a standard
Al2 O3 sample is shown in fig. 1 and that of Cu/Co thin film
multilayer is given in fig. 2.
Al2O 3
4000
(standard sample)
2000
Intensity (a. u.)
Counts/s
6000
0
[Cu 3nm/Co 2nm]10
Multilayer
30
20
40
60
80
100
40
45
50
55
60
2θ ( Degree )
120
2θ (deg. )
Fig. 1 : XRD pattern taken for Al2 O3 powder
sample.
35
Fig.2: XRD pattern of Cu/Co thin film
multilayer sample.
Mukul Gupta (mgupta@csr.res.in)
National Workshop on Interaction of ionizing Radiation with Biological systems
The Kolkata Centre of UGC-DAE Consortium of Scientific Research organized a two-day workshop on
“Interaction of ionizing Radiation with Biological systems” at Visva Bharati, Santiniketan during March 29-30,
2010. This thematic orientation workshop was organized in collaboration with the Department of Zoology, ViswaBharati, with a view to discuss the physico-chemical effects of ionizing radiation which are manifested as
malfunctioning of the biological systems at all levels of complexity - from unicellular, simple life forms to
multicellular higher organisms. The topics covered in the workshop included – Radiation and cellular response,
Radiation and Molecular biology, Radio-sensitisation and radio protection, Radiation genetics, Macromolecules of
biological importance, Growth and development, Radia tion carcinogenesis in the form of invited talks and
contributory presentations. There were more than 100 participants from various institutes and Universities of our
country. In all there were 13 invited talks and 4 contributory
presentations.
During the inaugural function Prof. S. K. Maitra,
Head Department of Zoology, Visva-Bharati welcomed all
the delegates. Prof. S. Bhattacharya, Emeritus Professor and
INSA Senior Scientist delivered the inaugural address
highlighting different aspects of radiation interaction with
living systems. Dr. A.K. Sinha, Centre-Director UGC-DAE
CSR KC presented an overview and scope of the workshop.
The keynote address delivered by Prof. A.R. Thakur, Vice
Chancellor West Bengal State University offered a vivid
illustration on reactions of different ionizing radiations with
living cells, free radical generation, relative sensitivity of
cells at different phases of cell cycle and DNA damage.
In the morning session of the first day, Prof. Sanghamitra Raha of SINP talked on radiation and adaptive
responses of living systems against radiation stress at molecular level and expression of survival genes. The
excellent deliberation of Dr Raha was followed by Dr T. Bandopadhay form VECC, who narrated about the
policies of radiation protection with special reference to Indian scenario. The post lunch session contained three
talks where the first speaker of the session, Dr D. Gupta from INMAS, New Delhi, discussed about oxidative stress
and cell signaling pathways as induced by ionizing radiation. His talk also included some disease pathology studies
in relation to radiation stress induction. A detailed view about metal induced radiation sensitization in heavy ion
irradiated microbes was presented by Dr Shaon Roy Chowdhury from West Bengal University of Technology,
Kolkata. The last speaker of the day was Dr S Dey from Calcutta University who discussed about radiation
protection by phyto-chemicals and its nano-compounds. A sight-seeing tour was organized by Visva-Bharati for all
the delegates and participants to visit all the heritage buildings and places of Tagore. The next had four technical
sessions. The first talk of the day was on the use of radio- pharmaceuticals with various radioisotopes in different
imaging techniques with especially used for cancer diagnosis and therapy, delivered by Dr S. K. Ganguly from
VECC. This was followed by two vivid presentations on immunological and endocrine effects of radiation on
mammals by faculties from Calcutta University and Guru Ghasidas University. In the second session of the day, the
illuminating presentation of Prof C. S. Chakraborty, (Vice Chancellor of West Bengal University of Fisheries and
Animal Sciences), covered important aspects of radiation genetics and the basic mechanisms thereof, highlighting
the scope of further research in this arena. Dr K. K. Mukherjee from Jadavpur University talked about chemical
protection of radiation induced DNA damage while Dr S. Roy from Burdwan University narrated role of
glutathione on DNA damage and repair as a function of radiation induced stress. CSR Scientists Dr A. Saha
discussed about the irradiation facilities of the Centre and VECC and highlighted the role of medium in modulation
of radiation induced damages and Dr A. Chakraborty presented an elaborate description of various stress responses
in relation to exposure to ionizing radiation and also briefed about the highlights of some of the ongoing programs
of the Centre in the field of radiation biology. The contributory papers of different universities threw light on the
current research trends in our country in the various fields of life sciences using different sources of radiation. Prof
Shelly Bhattacharya from Visva-Bharati gave an elaborative summary of the whole workshop in the concluding
session, which also saw a lively interactive session, with local and outstation participants.
The two day workshop directed towards identifying research areas of overlapping interest in the field of radiation
biology was brought to a successful culmination with the hope that this which could lead to collaborative research
programs from the universities and institutions.
Science Day 2010
Science Day was celebrated on 26th February at CSR, Indore centre. Two
lectures were arranged on this occasion. The first lecture was delivered by
Dr. Vasant Sathe, Scientist, CSR, Indore centre. He started with a popular
introduction to the lecture with unfolding the events and scientific aspects
that led to the discovery of Raman Effect on 28th February 1928. This is
followed by presentation of research work presently carried out at Raman
laboratory of CSR, Indore center. He discussed at length with many
examples the electronic Raman scattering and its importance in revealing
symmetry dependent energy gaps in superconductors and highly correlated
electron systems. He then illustrated low temperature (12 K) Raman scattering data on Ca(Sr)Cu3 Ti4 O12 samples
and contributions of electronic scattering in this system.
The second seminar was by Prof. Dinesh Varshney, School of Physics, DAVV, Indore, titled “Transport Properties
of Novel Materials”. He showed a number of examples of metal oxide compounds he has worked on including
mainly half metallic oxides, highly correlated electron materials and superconductors. He showed theoretical
simulation studies of phonon structure in these materials and compared them with experimental results.
The event was well attended by CSR, Indore faculty, staff and students as well as students from D.A.V.V.
Talks by CSR faculty / Students:
1. Study of interfaces in magnetic multilayers, Ajay Gupta, Indo-French Workshop on Magnetic Materials
including Spintronics, Varanasi, January 2010.
2. Spintronics Materials Thin Films: Problems and Prospects, R.J. Choudhary, at “National Seminar on
Physics and Evolution of Technology in the 21st Century” at Z G College, Calicut, 7-8 Jan 2010.
3. A series of four lectures on X-ray spectroscopic and neutron scattering studies of materials, A.V. Pimpale,
Department of Physics, RTM Nagpur University, Jan. 11-13, 2010.
4. Interaction of radiation with matter & Principles of radiation Detection at the UGC Refresher course in the
Thrust area “Nuclear Physics”, S S Ghugre, at University of Ranchi, January 12th and 13th 2010.
5. Synthesis and Biological Applications of Functionalized Luminescent Quantum Dots, A. Saha, in National
Workshop on Synthesis, Characterization and Applications of Nanomaterials held at Mahatma Gandhi
University, on January 12-14, 2010.
6. EDXRF- A tool for interdisciplinary research, M. Sudarshan, at The National Conference on X Ray
Fluorescence (XRF2010) at SINP, Kolkata Januaray 12-15, 2010.
7. Experiments at high magnetic field and at low temperatures, Alok Banerjee, JNCASR research conference
"Physics of New Materials" held in Kolkata from January 16-18, 2010.
8. Radiation Detectors & Their Applications in Pure & Applied Sciences, S S Ghugre, at the University of
Burdwan, January 17 2010.
9. Radiation Research in Biological Sciences, Anindita Chakraborty, at ICRPA 2010 at Burdwan University
January 17, 2010
10. In- field neutron diffraction experiments to probe magnetic transitions in rare-earth intermetallics and oxides,
V. Siruguri, Recent Advances in Correlated Electron Systems, IIT Guwahati, January 18-21, 2010.
11. Use of SQUID magnetometer, Alok Banerjee, one day mini-school on Thermal and Magnetic Studies in
Materials at UGC-DAE CSR, Kolkata Centre, on January 19, 2010.
12. Metastable states around 1st order transitions, P. Chaddah, Prof Anil Kumar Memorial Lecture at I I Sc
Bangalore, January 22, 2010.
13. Exotic Nuclei: key to the Elements in our Universe, A K Sinha, Homi J Bhabha’s Birth Centenary National
Conference on Frontiers in Physical Sciences, 23 January 2010, Department of Physics, Banaras Hindu
University, Varanasi.
14. Photo-conductivity analysis of nano-crystalline CdS using Conductive AFM, V. Ganesan, during the
“International Conference on MEMS and Optoelectronics Technologies, (ICMOT-2010)”, held at
Swarnandhra College of Engineering, Narasapur, Hyderabad during 22nd-23rd Jan. 2010.
15. Coexistence of contrasting magnetic phases and glassiness, Alok Banerjee, the Indo-French workshop on
Magnetism and Spintronics held during 28-31 January at Varanasi.
16. Neutron and X-ray scattering studies of materials, A.V. Pimpale, Annual Meeting of IAPT, Goa Chapter,
Carmel College, Goa, Jan. 30, 2010.
17. Luminescent Quantum Dots in Biological Interfacing, A. Saha, National Symposium on “Contemporary
Research in the Fields of Material Science and the Interface of Chemistry and Biology” held at University
of Allahabad, January 31-February 2, 2010.
18. Kinetically arrested long-range magnetic ordered phase, Alok Banerjee, the International Conference on the
Interaction, Instability, Transport and Kinetics: Glassiness and Jamming, Alok Banerjee, (IITK:GJ) held at
IIT, Kanpur during the February 4-8, 2010.
19. AFM and its emerging role in the field of nano-structures, V. Ganesan, at the National Conference on
"Current Trends in Material Sciences" held at Bhilai Mahila Mahavidyalaya, Bhilai during 5-6 February
2010.
20. X-ray photoelectron Spectroscopy, T. Shripathi, at refresher course at DAVV, school of Physics, in
February 2010.
21. Thin film facilities at CSR Indore, D.M. Phase, at Refresher Course at DAVV University, Feb 2010.
22. Thin film growth of materials, R.J. Choudhary, at Refresher course held at DAVV, Indore, 16th Feb 2010.
23. Spintronic Materials, R.J. Choudhary, at Refresher course held at DAVV, Indore, 18th Feb 2010.
24. Raman Spectroscopy, theory and application, Vasant Sathe, at refresher course at DAVV, school of Physics,
on 15-16 February 2010.
25. An outline of the same of the national facilities for research in nuclear physics and the study of n-rich light
nuclei, A K Sinha,at National Seminar on Nuclear Physics Research in India: Facilities & Perspectives, Feb
25-26, 2010, Dept of Physics, Raniganj Girls College, Raniganj, Burdwan.
26. Glass-like metastabilities across magnetic transitions - our results and some new concepts, P. Chaddah, at
IISER Pune, March 10, 2010.
27. Opportunities In Experimental Sciences With Low Energy Accelerators, A K Sinha, at National Workshop
on Low Energy Accelerators and Their Applications to Research and Industry, Department of Pure and
Applied Physics, GGV, Bilaspur, March 12-13, 2010.
28. Raman Scattering and its application in conference on Raman spectroscopy and its application, Vasant
Sathe, held at Dept. of Chemistry, M.S. University, Baroda on 13 March 2010.
29. X-ray Photoelectron Spectroscopy and its applications, T. Shripathi, at UGC Networking Winter School,
BHU, Varanasi March 15, 2010.
30. X-ray Imaging using refraction effe cts and its application in materials science and medical imaging, T.
Shripathi, at UGC Networking Winter School BHU , Varanasi March 16, 2010 .
31. Raman Spectroscopy, and EXAFS, Vasant Sathe, at Winter School by special UGC program for enrichment
of Research scholars held at Department of Physics, Banaras Hindu University, Varanasi on 17-18 March
2010.
32. X-ray Diffraction: Essentials to Experimental, Sudhindra Rayaprol, At National Workshop on X-ray
Diffraction: Techniques and Applications, held at Saurashtra University, Rajkot during March 17-19, 2010.
33. Application of Raman spectroscopy in nano structures, Vasant Sathe, at Department of Physics, Poona
University, Pune on 19 March 2010.
34. Exciting Aspects in Nuclear Science, A K Sinha, at annual technical festival- Cognizance 2010, Dept of
Physics, IIT-Roorkee, 26 March, 2010.
35. Magnetic Circular Dichroism (MCD): Introduction and some typical results, Alok Banerjee, in the two days'
Seminar on the theme 'Trends in condensed matter physics' held during March 26 - 27, 2010 in the
University of Rajasthan, Jaipur.
36. Thin films x-ray diffraction, Raghavendra Reddy, at National Workshop on X-ray Diffraction Techniques
and Applications (NWXRD-2010) during March 2010 held at Saurashtra University,Rajkot.
37. Understanding the Ano malous physical properties of nanocrystalline nickel, G. S. Okram, at School of
Physics, Devi Ahilya University, Indore, 27 March 2010.
38. Irradiation Facility and Medium-Mediated Effects: A Brief Description, A. Saha, in National Workshop on
Interaction of Ionizing Radiation in Biological Systems held at Visvabharati , March 29-30, 2010.
39. Stress response of biological systems exposed to ionizing radiation, Anindita Chakraborty, in National
Workshop on Interaction of Ionizing Radiation in Biological Systems held at Visvabharati , March 29-30,
2010.
40. Evolution of the physical properties of nano- nickel, G. S. Okram, Raja Ramanna Centre for Advanced
Technology, Indore, April 8, 2010.
41. Recent understanding on the physical properties of nanocrystalline nickel, G. S. Okram,, Department of
Metallurgical Engineering and Materials Science, Indian Institute of Technology, Bombay, Mumbai, June
10, 2010.
42. Anomalous magnetostriction and magnetoresistance in Gd 5 Ge3, oral presentation by Ms. Pallavi Kushwaha
at Recent Advances and Strongly Correlated System held at IIT, Guwahati
Talks at CSR:
1. Giant superconductivity- induced modulation of the ferromagnetic magnetization in a cuprate- manganite
superlattice, Jochen Stahn, ETH Zurich and Paul Scherrer Institut, Villigen Switzerland, Jan 25, 2010.
2. Magnetism and Crystal Field Effect in Pr-Compounds, Vivek Kumar Anand, TIFR Mumbai, Feb. 11, 2010
3. Many-Body Correlations in Single and Coupled Quantum Wires, R.K. Moudgil, Kurukshetra University,
Mar. 6, 2010.
4. Magnetism and Magneto-Transport Properties of Half Metallic Ferromagnet CrO 2 - A Potential Material for
Spintronics, A.K. Nigam, TIFR Mumbai, Mar. 15, 2010.
5. Crystal growth and anisotropic magnetic properties of rare-earth intermetallic compounds, A. Thamizhavel,
TIFR Mumbai, Apr. 30, 2010.
6. Scanning Probe Microscopy of Complex Materials, C.V. Dharmadhikari, University of Poona, May 14,
2010.
7. Thermo-responsive Microgel Dispersions: Dynamics and Phase Behaviour, B.V.R. Tata, IGCAR,
Kalpakkam, July 9, 2010.
Foreign Visits by Faculty and Students of CSR:
1. Dr. Dileep Kumar visited synchrotron radiation at Photon factory, Tsukuba, Japan during March 18th to 18th
April, 2010.
2. Ms. Swati Pandya, SRF, visited Washington DC, USA to present her work at the 11th Joint MMM – Intermag
conference during Jan 18-22, 2010, and for an oral presentation.
3. Prof. Ajay Gupta visited Photon Factory, JAPAN during April 17-28, 2010.
4. Dr. T. Shripathi visited PETRA III, DESY, Germany during May 16-25, 2010 for carrying out experiments.
5. Ms. Shreeja Pillai (JRF) visited PETRA III, DESY, Germany during May 16-25, 2010 for carrying out
experiments.
6. Dr. V. Siruguri visited Helmholtz Zentrum Berlin (formerly Hahn Meitner Institute, Berlin) from June 23 – July
4, 2010 for carrying out neutron diffraction experiments.
7. Dr. S. Rayaprol visited Helmholtz Zentrum Berlin (formerly Hahn Meitner Institute, Berlin) from June 23 –
July 4, 2010 for carrying out neutron diffraction experiments.
Awards and Recognitions:
1. Staff:
Dr. S.R. Barman received Materials Research Society of India (MRSI) medal (2010).
3. Users:
1.
Mr. Amit Khare, Department of Physics, Barkatullah University, Bhopal, bagged the Young Scientist Award
for his work “Study of the effect of Ce doping in La 0.7Ca0.3 MnO3 ” presented during Silver Jubilee Young
Scientist Congress held at Vigyan Bhawan during 22-23 February, 2010 by Madhya Pradesh Council of Science
and Technology, Bhopal. The work involved extensive use of CSR facilities.
2. Ms. Rujuta R. Doshi Department of Physics, Saurashtra University, RAJKOT was awarded Best Oral
Presentation Award at “International Conference on Nanoscience and Nanotechnology” held during February
24-26, 2010 at SRM University, Chennai jointly organized by SRM University, Chennai and IGCAR,
Kalpakkam, for her presentation on “Size Dependent Magnetotransport in Nanostructured Manganites”. All the
measurements involved in the presentation were carried out at UGC-DAE CSR Indore.
3. Prof. R. Brar, Department of Instrumentation Sciences, Jadavpur University, Kolkata, received 3rd best poster
presentation award in the Biological field at the International Conference on Advances in Electron Microscopy
and Related Techniques & XXXI Annual Meeting of EMSI, held during March 8-10, 2010, at BARC, Mumbai.
The work involved extensive use of CSR facilities
The following research students have received their senior research fellowships from CSIR based on work
done at the Consortium:
1.
2.
3.
4.
Ms. Srabanti Ghosh in Year 2009-2010
Ms. Bhavya Bhushan in Year 2010-2011
Mr. Amit Kumar Mishra in Year 2010-2011
Ms. Ritwika Chakraborti in Year 2010-2011
PhD awards :
1.
Mr. Kaustav Mukherjee has been awarded Ph.D degree from DAVV under the supervision of Dr. Alok
Banerjee. Thesis title: “Magnetic and transport properties of different manganese oxides and their relation
with the structures and electronic states”
2.
Ms. Aditi Dubey has been awarded Ph.D. degree from DAVV under the supervision of Dr. Vasant Sathe.
Thesis title: “Phase transition studies by Raman scattering on oriented oxide thin films”.
3.
Ms. Deepti Jain has been awarded Ph.D. degree from DAVV under the supervision of Dr. V. Ganesan.
Thesis Title: “Physical and morphological studies in potential systems of biological interest”.
4.
Ms. Aparna Datta has been awarded to Ph.D. (Science) degree of Jadavpur University under the supervision
of Dr. Abhijit Saha and co-supervision of Prof. K. K. Mukherjea. Thesis title: “Synthesis of CdS
Nanoparticles in Aqueous and Organic Phase by Chemical and Radiolytic Techniques and its Possible
Interactions with Molecules of Biological Relevance”
Two views of the building which will house the Kalpakkam node that is nearing completion. The
instruments are expected to be commissioned shortly and the node is expected to become functional
early next year. For details contact Dr. G. Amarendra (e- mail: ga@csr.res.in).
Edited by: Dr. T. Shripathi