Poster session C - Multiferroics
P.163 Neutron powder diffraction study of magnetic structure of Mn
1-x
Cu x
WO
4
(x=0.025-0.2)
N K Chogondahalli Muniraju, Y Xiao, M Ohl, T Chatterji and T Brückel
Forschungszentrum Jülich, JCNS-SNS-ORNL, Germany
Abstract unavailable
P.164 The role of doped La for anomalous 2D-ferromagnetic cluster phase of Ho
0.8
La
0.2
Mn
2
O
5 multiferroic
H Chou 1 , C P Wu 1 , S R Yah 1 , K S Yang 1 , C-W Wang 2 , W-H Li 2 , J M Chen 3 and J J Lee 3
1 National Sun Yat-sen University, Taiwan, 2 National Central University, Taiwan, 3 National Synchrotron Radiation
Research Center, Taiwan
The crystal and magnetic structures, especially the anomalous 2D ferromagnetic phase at 80~190K, of
Ho
0.8
La
0.2
Mn
2
O
5 were investigated by high resolution neutron powder diffraction and the X-ray absorption spectra.
Within this specific temperature range 80~190K, 20% La doping on the Ho sites triggers a series structure distortion and charge redistributions that are strongly associated with the formation of the dynamic 2D ferromagnetic clusters. The average local structure changes, such as the Mn-Mn distances and Mn-O-Mn bond angles suppressed, indicates that it is possible enhancing the possibility of ferromagnetic coupling between
Mn
Octahedral
and Mn
Pyramid
along the b-axis direction while reducing in the a-axis direction. Bond valence analysis reveals charge redistribution promoting the valences of Mn
Octahedral
and Mn
Pyramid
to be closer to Mn 4+ and Mn 3+ within the specific temperature range, respectively. The temperature evolutions of X-ray absorption spectra reveal the difference roles of rare earth series La and Ho ions and the doping of larger nonmagnetic ions La triggers deformations mentioned above and provides an opportunity for a magnetic coupling among Ho and Mn whenever a
La ion locates nearby. These possible ferromagnetic coupling sites are much more than those contribute to ferromagnetic signals, indicating only part of these sites become ferromagnetically by the assistance of the thermal phonon within this specific temperature range.
P.165 On the magnetic structure of multiferroics EuMn
2
O
5
, Tb
1-x
Ce x
Mn
2
O
5
:XYZ-polarization analysis
E Dimakova, Z Igor, P Vladimir and G Sergey
PNPI, Russia
The XYZ-polarization analysis evidences in favor of the spiral magnetic structure for all compounds studied. In
EuMn
2
O
5
, at 4 K the magnetic moments ordered in the plane, which makes an angle of ~ 40° with ab plane. With temperature increasing this angle increases also and at 25 K it makes up 70°.
For the compound Tb
0.8
Ce
0.2
Mn following way: below T
N
2
O
5 we find out that the temperature evolution of the magnetic phases goes in the
≈ 39 K there is the commensurate propagation vector k
1
= [0.5 0 k z1
], with k z1
= 0.25, which remains down to 15 K when cooling, after that changes gradually to the value 0.28. At 20 K (when cooling!) the appearance of the second magnetic phase was observed with non-commensurate magnetic propagation vector k
2
[0.5 0 k z2
]. The value of k z2
changes in temperature region 20K – 15K from 0 to 0.292, then remains permanent down to 1.5 K. Thus, in the wide temperature region two magnetic phases do coexist.
=
The essential temperature hysteresis in this system was observed. At heating k z1
,k z2 components return to their high temperature values at the temperatures significantly different from those upon cooling – the difference is about 7 K.
ICNS 2013 International Conference on Neutron Scattering

In pure TbMn
2
O
5
three magnetic phases were observed and they coexist in very narrow temperature region; the temperature region of coexistence also depends in some extent on the temperature pre-history.
P.166 Competing magnetic orders and ferroelectric phases in multiferroic Mn
1-x
CoxWO
4
J L Garcia-Muñoz 5 , I Urcelay-Olabarria 1 , E Ressouche 2 , A A Mukhin 3 , V Yu. Ivanov 3 and V Skumryev 4
1 Institut Laue-Langevin, France, 2 Institut Laue-Langevin, France, 3 Prokhorov General Physics Institute of the Russian
Academy of Science, Russia, 4 Institut Català de Recerca i Estudis Avançats (ICREA), Spain / Universitat Autònoma de Barcelona, Spain, 5 Institut de Ciència de Materials de Barcelona, Spain
In the reference MnWO
4
frustrated multiferroic magnetic and ferroelectric orders coexist and mutually interact. It undergoes three successive magnetic phase transitions. Below 13.5 K the AF3 phase is incommensurate and paraelectric. In the AF2 phase (7.5 K < T < 12.5 K) a spontaneous polarization along b axis coexists with a cycloidal spin order (k=(-0.214, 1/2, 0.457)). Below 7.5 K the system is collinear commensurate (k = (±1/4, 1/2,1/2),
AF1)). Addition of Co +2 ions enhances the role of magnetic anisotropy in the system leading to a rich Mn
1-x
Co x
WO
4 phase diagram [1-3]. We have studied a variety of magnetic and ferroelectric phase transitions induced by temperature or magnetic fields in Mn
1-x
Co x
WO
4
multiferroics by single crystal neutron diffraction and polarization measurements. The competition between magnetic anisotropy and isotropic exchange interactions gives rise to a diversity of competing multiferroic magnetoelectric phases with complex noncollinear magnetic orders. Varying the
Co content precise magnetic structures have been determined as a function of temperature and under field
(collinear, commensurate, incommensurate cycloidal, conical orders, ..). The compatibility of the structure, magnetic symmetry and polarization anisotropy has been analyzed in this family.
[1] Y.-S. Song et al, Phys. Rev. B 82, 214418 (2010).
[2] K-C Liang et al, New Journal of Physics 14 (2012) 073028.
[3] I. Urcelay-Olabarria et al, Phys. Rev. B 85, 094436 (2012); also Phys. Rev. B 85, 224419 (2012), Phys.
Rev. B 86, 184412 (2012), Phys. Rev. B 87, 014419 (2013).
P.167 Magnetic and ferroelectric transitions in Mn
0.8
Co
0.2
WO
4
: transverse conical antiferromagnetic order and polarization
J L Garcia-Muñoz 4, I Urcelay-Olabarria 1 , E Ressouche 1
Muñoz 4
, A A Mukhin 2 , V Yu. Ivanov 2 , V Skumryev 3 and J L Garcia-
1 Institut Laue-Langevin, France, 2 Prokhorov General Physics Institute of the Russian Academy of Science,
Russia, 3 Institut Català de Recerca i Estudis Avançats (ICREA), Spain / Universitat Autònoma de Barcelona,
Spain, 4 Institut de Ciència de Materials de Barcelona, Spain
Evolution of competing commensurate collinear (AF4) and incommensurate cycloidal (AF2) spin structures in
Mn
0.8
Co
0.2
WO
4
multiferroic was studied by neutron diffraction, magnetic, and pyroelectric characterization measurements. In contrast to pure and slightly Co doped MnWO wave vector k
1
=(0.5, 0, 0) inherent to the pure CoWO
4
4
, the antiferromagnetic AF4 collinear phase with
was observed below T
N
≈ 20 K in Mn
0.8
Co
0.2
WO
4
. This collinear order survives down to the lowest temperature reached in the experiments (2 K) even after the appearance of the second (cycloidal AF2) spin order below T
FE was revealed below T
FE
≈ 8.5 K [k
2
=(0.211, 0.5, 0.452)]. Ferroelectric polarization along b-axis
in the low temperature conical phase resulting from the superposition of the AF4 and AF2 spin structures. of the AF4 and AF2 spin structures. The arrangement of the spins after the two successive magnetic transitions are thoroughly described. In particular, we found that spins in the AF4 phase are aligned along the easy direction in the ac-plane (~142 o with respect to the c*-axis), while the cycloidal AF2 spin order is developed in the magnetically hard directions, perpendicular to the easy one. The relevance of this spin order for the observed behavior of the electric polarization is analyzed and compared with the ferroelectric properties in the pure MnWO
4
.
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[1] M. Kenzelmann et al, Phys. Rev. Lett. 95, 087206 (2005)
[2] F. Yeet al, Phys. Rev. B 83, 140401(R) (2011)
[3] I. Urcelay-Olabarria et al, Phys. Rev. B 85, 094436 (2012)
[4] I. Urcelay-Olabarria et al, Phys. Rev. B 85, 224419 (2012)
P.168 Phonons in multiferroics YMnO
3
and GaFeO
3
: Inelastic neutron scattering and first principles studies
M Gupta 1 , R Mittal 1 , N Sharma 1 , R Singh 1 , S Chaplot 1 , M Zbiri 2 , S Rols 2 and H Schober 2
1 Bhabha Atomic Research Centre, India, 2 Institut Laue-Langevin, France
We report phonon density of states in GaFeO
3
and YMnO
3
using IN4 time of flight spectrometer at ILL from 50 K to
1300 K, covering the magnetic and structural transitions in these compounds. The measured spectra on cooling across the magnetic transition temperature indicate increase in intensity of the low energy phonons around 20 meV associated with the Fe and Mn atoms. The low energy vibrations in both the compounds show significant Q dependence up to about 850 K. This indicates that although magnetic transition temperature for GaFeO
3
and YMnO is around 225 K and 70 K respectively, paramagnetic spin fluctuations persists up to very high temperatures. We have not found any significant change in the phonon spectra on heating across the first order paraelectric
3
(P6
3
/mmc) to polar phase (P6
3 cm) transition in YMnO
3 at 1243 K. GaFeO
3 does not show any structural phase transition at high temperature. However increase in distortion of various polyhedral units might be the reason for gradual broadening of stretching modes around 60 meV. Ab-initio phonon calculations in various phases of these compounds are used to understand the spin-lattice coupling. The free energy calculations in various phases indicate that loss of iron magnetic moment leads to high pressure structural phase transitions in these compounds.
P.169 A magnetic and crystal structure studies on BaXO
3
(X = Mn, Ti) mixed BiFeO 3 multiferroic
S J Kim and S Lee
KAERI, Korea
BiFeO
3
(BFO) is well known room temperature multiferroic material with 640K of Neel temperature and 1100K of
Curie temperature. One of the disadvantages of BFO is large leakage current. There has been study to reduce leakage current by adding donor materials in BiFeO
3
(BFO). BaXO
3
(BXO, X = Mn, Ti)is used for one of donor source.
We grow BFO-BXO single crystal using flux method. The crystal and magnetic structure as functions of temperature were investigated using X-ray and Neutron diffraction. The crystal structure of single crystal shows some differences from previously reported ceramic system. The magnetic structure of BFO+BXO can be described by G-type antiferromagnetic order without spiral magnetic order at room temperature. We will discuss the correlation between spin structure and iso-structural change of mixed BFO single crystal.
P.170 Magnetism and ferroelectricity in multiferroic Tm
1-x
Yb x
Mn
2
O
5
single crystals
H Kimura 1 , K Yamazaki 1 , T Nakano 1 , M Fukunaga 2 , Y Noda 1 , T Ishigaki 3 , I-H Oh 4 and C H Lee 5
1 Tohoku University, Japan, 2 Okayama University, Japan, 3 Ibaraki University, Japan, 4 KAERI, Korea, 5
Tohoku University, Japan
KAERI, Korea /
RMn
2
O
5
(R = rare-earth, Bi, Y) is one of the prototypical multiferroics in which the electric polarization is induced by a long-period magnetic order. The system shows successive magnetic transition from high-temperature incommensurate magnetic (HTICM) phase to low-temperature incommensurate magnetic (LTICM) phase thorough commensurate magnetic (CM) phase as temperature decreases. With decreasing ionic radii of R 3+ ions by changing rare-earth site from Bi 3+ to Lu 3+ , the intermediate CM phase disappears, of which critical point locates between
TmMn
2
O
5
and YbMn
2
O
5
. The competition between the (HT,LT)ICM phase and the CM phase is governed by the
ICNS 2013 International Conference on Neutron Scattering

competing magnetic interactions acting on between Mn 3+ spins and Mn 4+ spins, which provides various types of ferroelectricity in this system. However, it has been not clarified how the competing interactions contribute to the magnetic phase diagram as well as what is the microscopic relation between the CM (ICM) phase and the x ferroelectricity. Therefore we have measured dielectric property and microscopic magnetism of composite Tm
1-
Yb x
Mn
2
O
5
single crystals to elucidate where the CM phase disappears and what happens on the magnetism and ferroelectricity at the critical point.
The present neutron diffraction study confirms that the CM phase survives up to x = 0.9 but the volume fraction of the CM phase is quite small. On the contrary, LTICM phase becomes robust with increasing x. The permittivity and pyro-current measurements are now in progress. The magnetic and dielectric phase diagram as functions of temperature and Yb 3+ composition x will be presented at the conference.
P.171 A neutron diffraction study of the magnetic structure of NdMn
2
O
5
A Kuncevich 1 , I Zobkalo 2 , S Gavrilov 2 , S Barilo 3 and S Shiryaev 3
1 Petersburg State Polytechnical University / PNPI, Russia, 2 National Research Centre, Egypt, 3 Scientific-Practical
Materials Research Centre NAS of Belarus, Belarus
The neutron scattering investigations of the magnetic orderinginNdMn
2
At T
N k z1
), k
2
= (0.5 0 k z2
). The k z1
, k z2
O
5 have been performed on the single crystal.
≈ 30 K the onset of the long-range magnetic ordering with incommensurate wave vector k = (0 0 ~0.36) is observed. Below 30 K two magnetic phases are observed with propagation vectors close each other - k
1
= (0.5 0
components increase monotonously with temperature decrease down to 25 K, then remain to be constant with values k z1
= 0.384(2), k z2
= 0.395(2). The peculiarity in the temperature dependencies of the integrated intensities of magnetic scattering at 18 - 20 K evidences about one more magnetic transition. Our results indicate the effect of the rare earth ion size on the exchange interactions in the RMn
2
O
5
.
P.172 Structural anomalies at the commensurate-incommensurate transition of multiferroic YBaCuFeO
5
M Medarde 1 , M Morin 1 , G Deng 2 , D Sheptyakov 1 , L Keller 1 , A Scaramucci 3 , N Spaldin 3 , M Kenzelmann 1 , E
Pomjakushina 1 and K Conder 1
1 Paul Scherrer Institut, Switzerland, 2 Bragg Institute, ANSTO, Australia, 3 Materials Theory, ETH Zurich, Germany
Abstract unavailable
P.173 Low temperature magnetic structure of multiferroic YBaCuFeO
5
M Morin 1 , E Pomjakushina 1 , D Sheptyakov 1 , L Keller 1 , J Rodriguez-Carvajal 2 , A Scaramucci 3 , N Spaldin 3 , M
Kenzelmann 1 , K Conder 1 and M Medarde 1
1 Paul Scherrer Institut, Switzerland, 2 Institut Laue Langevin, France, 3 Materials Theory, ETH Zurich, Germany
The discovery of materials where magnetic and ferroelectric orders are strongly coupled has raised a great deal of interest in view of its possible use in data storage technologies. Unfortunately, their promising technological multifunctionalities -such as the control of electric polarization with magnetic fields - usually occur at temperatures too low for most practical applications (typically T <20-40K).
The oxygen-deficient double perovskite YBaFeCuO
5
constitutes a remarkable exception. Magnetism-driven ferroelectricity has been recently reported to exist below T
C
= 220K coinciding with the occurrence of a commensurate - to - incommensurate reorientation of the Fe 3+ and Cu 2+ magnetic moments [1]. From a more fundamental point of view the observation of incommensurable magnetic order in this material at such high
ICNS 2013 International Conference on Neutron Scattering

temperatures is rather surprising. In particular, the nature of the relevant competing magnetic interactions and its possible link to low dimensionality or geometrical frustration is not understood at present.
The existence of magnetic order in YBaCuFeO
5
below 440K is known since 1995 [2] but the low-temperature incommensurate magnetic structure (T < 220K) has not yet been solved. Here we report novel neutron powder diffraction data which enabled us to propose a model that satisfactorily describes the magnetic intensities between
1.5 and 220K [3]. The implications for the polarization direction and the magnetoelectric coupling in this material are discussed.
[1] B. Kundys et al., Appl. Phys. Lett. 94, 072506, (2009).
[2] V. Caignaert et al., J. Solid State Chem. 114, 24, (1995).
[3] M. Morin et al., in preparation
P.174 Magnon contribution to the specific heat of (Y/Lu)MnO
3
estimated from inelastic neutron scattering data
J Oh 1 , J Jeong 1 , K Nakajima 2 , S Ohira-Kawamura 2 and J-G Park 1
1 IBS Research Center for Functional Interfaces and Correlated Electron Systems, Seoul National University, Korea,
2 J-PARC Center, Japan Atomic Energy Agency, Japan
Hexagonal manganites RMnO
3
(R=rare-earth ions) are one of most extensively studied multiferroics and exhibit effects due to magnetic frustration arising from a two dimensional triangular lattice. A coupling between the ferroelectric and magnetic order parameters was borne out by several physical properties such as the dielectric constant and thermal expansion coefficient, to name only a few.
Below the antiferromagnetic transition temperature, the magnetic specific heat of (Y/Lu)MnO
3
exhibits broad features apart from the lamba-like anomaly due the antiferromagnetic ordering [1],[2]. Although a couple of scenarios including a spin reorientation transition have been so far put forward, none of them seems to be able to explain the anomaly correctly.
In this report, we performed inelastic neutron scattering experiments to explain the anomaly in terms of magnon entropy. We carried out our experiments using powder samples of (Y/Lu)MnO
3
at the AMATERAS beamline at J-
PARC. In order to obtain the magnetic DOS from the experimental data, we have corrected our raw data for the dynamical structure factor, calculated using a model Hamiltonian consistent with the measured spin waves. The magnetic specific heat then calculated using the obtained DOS is found to explain the broad feature in the measured magnetic specific heat not only qualitatively but also quantitatively. Based on this analysis, we conclude that the origin of the broad feature in the specific heat is due to the Debye-like contribution of magnon.
[1] D. G. Tomuta et al., J. Phys.: Condens. Matter 13 4543-4522 (2001)
[2] J. Park et al., Phys. Rev. B 82, 054429 (2010)
P.175 Experimental study of the possible Multiferroic magnetoelectric NaLnMM’O
6
family
B Orayech 1 , G A López 1 , O Fabelo 2 , L Elcoro 1 , A Faik 3 and J M Igartua 1
1 Universidad Del País Vasco (UPV/EHU), Spain, 2 Institut Laue-Langevin (ILL), France, 3 Research Institute of Solar
Energy and New Energies (IRESEN), Morocco
Some materials with the general formula AA’BB’O
6
, double perovskites with a layer ordering of the A and A’ site cations, have been proposed to show Multiferroic Magnetoelectric properties (MMP). With that ordering, the highest possible symmetry is described by the P4/nmm (#129) space group, which has the polar P2
1
Thus, in those materials ferroelectricity is allowed theoretically and experimentally, if P2
1
(#4) as a subgroup.
could be found to exist.
The presence of a magnetic cation will give rise to magnetic properties, that could couple to the electric ones, giving rise to the MMP. We have synthesised some new materials with the A-site layer arrangement: NaLnMWO
6
ICNS 2013 International Conference on Neutron Scattering

(Ln=La,Nd,Pr) and (M=Co,Ni,Mn) and NaLaMTeO
6
(M=Co,Ni,Mn,Mg). We have analysed them by laboratory X-Ray
(XRPD), some by synchrotron radiation diffraction, by neutron powder diffraction (NPD) and by SEM and by TEM.
We present SEM images, to show the homogeneity and purity of the samples; the XRPD data, compatible with the usually assumed double perovskite cell and layered ordering; we present a set of TEM images which reveal three types of long-order arrangements; we present the NPD results for some of the compounds. Our aim is to describe theoretically the experimentally observed long-order arrangements at room-temperature in some of the compounds and explore the possible presence of temperature induced phase transitions.
P.176 Magneto-orbital helices: A novel route to coupling magnetism and ferroelectricity in multiferroic CaMn
7
O
12
N Perks 1 , R Johnson 1 , C Martin 3 , L Chapon 4 and P Radaelli 1
1 University of Oxford, UK, 2 University of Oxford/ISIS facility, UK, 3 Laboratoire CRISMAT, France, 4 Institut Laue-
Langevin, France
Multiferroic materials, specifically those possessing a magnetically induced improper ferroelectric polarisations attract considerable interest, due to both their novel physics, and their potential technological application, exploiting cross coupling of electrical properties. Work presented here forms part of a wider effort to develop strongly coupled, high temperature multiferroics with enhanced functionality.
Orbital physics drives a rich phenomenology in transition metals, providing microscopic underpinning for effects such as colossal magnetoresistance. Magnetic and lattice degrees of freedom are coupled through orbital ordering, and it has long been hoped that this coupling could be exploited to create new multiferroic materials. Here, we report an unprecedented magneto-orbital texture in multiferroic CaMn
7
O
12
, giving rise to the largest magnetically induced polarisation measured to date. Neutron and x-ray diffraction has characterised magnetic and structural modulations, which are intertwined to form an ‘incommensurate magneto-orbital helix’. Analysis of magnetic exchange shows that orbital order is crucial in stabilising the chiral magnetic structure, subsequently allowing for electric polarisation. The presence of a global structural rotation promotes the coupling between this polarisation and magnetic helicity required for multiferroicity. These observations open up the possibility of finding a new class of strongly coupled multiferroic materials, underpinning their technological development.
P.177 Spin reorientation effect in Fe doped YMnO
3
N Sharma, A Das, C Prajapat and S S Meena
Bhabha Atomic Research Centre, India
Abstract unavailable
P.178 Long- and short-ranged structure of multiferroic Pb(Fe
0.5
Nb
0.5
)
O3
H Sim 1 , S Lee 2 , K-P Hong 2 , S Lee 3 , T Kamiyama 4 , T Otomo 4 , S-W Cheong 5 and J-G Park 2
1 Seoul National University, Korea, 2 IBS Research Center for Functional Interfaces and Correlated Electron Systems,
Seoul National University, Korea, 3 Neutron Science Division, Korea Atomic Energy Research Institute,
Korea, 4 Institute of Materials Structure Science & J-PARC Center (KEK), Japan, 5 Rutgers University, USA
Lead iron niobate Pb(Fe
0.5
transition at T
N
Nb
0.5
)O
3
(PFN) is a multiferroic disordered system. It has a G-type antiferromagnetic
= 143 K and a ferroelectric transition at T
C
= 385 K. Its reported high dielectric constant makes it a suitable candidate material for multilayer ceramic capacitors as well as other electronic devices. Despite the interesting properties, however there is still controversy over the room temperature structure: for example, two competing space groups of R3m and Cm structure have been so far proposed. More importantly, it is not clear
ICNS 2013 International Conference on Neutron Scattering

whether this material has Pb-disorder. More recently, it was reported to have interesting negative thermal expansion behavior below the antiferromagnetic transition.
In order to understand the properties better and resolve some of the controversies, we carried out both high resolution neutron powder diffraction and total scattering experiments using S-HRPD and NOVA beamlines of J-
PARC, respectively. By taking advantage of the data, we could analyze both long-ranged and short-ranged structures systematically.
For example, we found that there is no negative thermal expansion behavior below the antiferromagnetic transition by carefully examining the S-HRPD data. Our high resolution S-HRPD data also showed that the thermal parameter of Pb ion is unusually large, indicative of the existence of static disorder at the Pb site. This observation is corroborated by our total scattering analysis using the NOVA data.
P.179 Study of direct relations between the spiral spin ordering and ferroelectric polarization in multiferroic Mn
1x
Co x
WO
4
Y-S Song 1 , J-H Chung 1 , S-B Kim 2 , J Schefer 3 , S-H Chun 4 , B Lee 4 and K H Kim 4
1 Korea University, Korea, 2 Konyang University, Korea, 3 Paul Scherrer Institut, Switzerland, 4 Seoul National University,
Korea
Magnetoelectric multiferroics refer to materials in which ferroelectricity and (ferro)magnetic ordering are simultaneously observed and often exhibit strong coupling. Such coupling between (ferro)magnetic and ferroelectric order is known as magnetoelectric effect. MnWO
4
is one of the best studied magnetoelectric multiferroics. In this material, ferroelectric polarization (P) is observed only in the elliptical spiral incommensurate antiferromagnetic spin order (AF2 phase, 7.6 K < T < 12.7 K, P || b), but not in the collinear commensurate (AF1 phase, T < 7.6 K) or the collinear incommensurate (AF3 phase, 12.7 K < T < 13.5 K). The major direction of the ferroelectric polarization on the AF2 phase can be explained based on the spin current model, i.e. P = Ae ij doping effect on the magnetic structures of multiferroic Mn
1-x
Co x
WO
4
×(S i
×S j
). We investigated the Co
using neutron diffraction experiments. The main results are that the noncollinear spiral AF2 is stabilized down to the base temperature in replacement of the AF1 when the Co substitution increases up to x ~ 0.05, and the spiral planes of the AF2 becomes perpendicular to the b axis for x = 0.10 ~ 0.15. This spin-flop transition is accompanied by the flop of the ferroelectric polarization, upon which the primary orientation of P is along the a axis. For x = 0.20, however, the spiral planes and the main P direction reverts back to the b axis. All these results indicate that the magnetoelectricity of Mn
1-x
Co x
WO
4
can be explained by the spin current model, and it can be controlled via Co doping. We will propose and discuss a model including two competing anisotropies, which can successfully explain the doping dependence of the magnetic ordering.
P.180 Magnetically induced texture in CaMn
7
O
12
studied with neutron powder diffraction
M Stekiel 1 , D Wardecki 1 , R Przenioslo 1 , W Slawinski 1 , I Sosnowska 1 and L Keller 2
1 University of Warsaw, Poland, 2 Pauls Scherrer Institute, Switzerland
The measurements of neutron powder diffraction have been performed with the multiferroic CaMn
7
O
12
system which shows magnetoelectric and magnetoelastic couplings [1-4]. The measurements were performed by using the diffractometer DMC at SINQ. The measurements performed at T=3K without magnetic field show a modulated magnetic ordering that can be described with two incommensurate modulation vectors in agreement with our earlier studies [5]. The Vanadium container was not totally filled with the powder sample so the crystallites had free space to move. A texture effect was observed when the magnetic field was turned on. The intensity ratio of some selected Bragg peaks change gradually with increasing magnetic field strength. The neutron diffraction patterns can
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be explained by assuming a gradual rotation of the crystallites towards the easy magnetization axis. A quantitative model of this effect is presented.
[1] R. Przeniosło, I. Sosnowska, D. Hohlwein, T. Hauss and I.O. Troyanchuk, Solid State Comm. 111 (1999)
687.
[2] G. Zhang, S. Dong, Z. Yan, Q. Zhang, S. Yunoki, E. Dagotto and J.-M. Liu, Phys. Rev.B84 (2011) 174413.
[3] R.D. Johnson, L.C. Chapon, D.D. Khalyavin, P. Manuel, P.G. Radaelli, and C. Martin,Phys. Rev. Lett. 108
(2012) 067201.
[4] W. Sławiński, R. Przeniosło, I. Sosnowska, M. Bieringer, I. Margiolaki and E. Suard, Acta Cryst. B65 (2009)
535.
[5] W. Sławiński, R. Przeniosło, I. Sosnowska and A. Chrobak, J. of the Phys. Soc. of Japan. 81 (2012)
094708.
P.181 Multiferroicity in the generic easy-plane triangular lattice antiferromagnet RbFe(MoO
4
)
2
J S White 1 , Ch. Niedermayer 1 , G Gasparovic 2 , C Broholm 2 , S Park 3 , E Ressouche 4 , A Ya. Shapiro 5 , L N Demianets 5 and M Kenzelmann 1
1 Paul Scherrer Institut, Switzerland, 2 The Johns Hopkins University, USA, 3 HANARO Neutron Facility,
Korea, 4 CEA/Grenoble, France, 5 A.V. Shubnikov Institute for Crystallography RAS, Russia
RbFe(MoO
4
)
2
is two-dimensional (2D) triangular lattice antiferromagnet (TLA) that displays a zero-field magneticallydriven multiferroic phase with a chiral spin structure. We have employed neutron scattering in order to complete the picture of the microscopic magnetism across the phase diagram. By inelastic neutron scattering in zero magnetic field, we have determined quantitatively the spin Hamiltonian, and show that the easy-plane anisotropy is nearly
1/3 of the dominant spin exchange. This makes RbFe(MoO
4
)
2
a model material for experimental studies of the generic properties of the 2D easy-plane TLA. We explored the phase diagram via elastic measurements under both easy-axis and easy-plane magnetic fields. For easy-axis fields, due to the large XY anisotropy no magnetic phase transitions or symmetry changes are observed for fields up to 12 T, and thus indicate a persistent multiferroic chiral state. For large easy-plane fields, the phase diagram is richer, and our measurements provide direct evidence that both quantum and thermal fluctuations stabilize the generic finite-field phases in this material. Furthermore, we show that the previously unstudied magnetic structure in the high-field incommensurate phase does not feature chirality, and so its properties are consistent with a bulk paraelectric state. We conclude that multiferroicity in
RbFe(MoO
4
)
2
, or its absence under high in-plane fields, is a direct consequence of the generic properties of the model 2D XY TLA.
P.182 Direct-coupling of ferromagnetism and ferroelectricity by multi-component magnetism Mn
2
GeO
4
J S White 1 , T Honda 2 , T Kimura 2 , Ch. Niedermayer 1
Kenzelmann 1
, L C Chapon 3 , O Zaharko 1 , A Poole 1 , B Roessli 1 and M
1 Paul Scherrer Institut, Switzerland, 2 Osaka University, Japan, 3 Institut Laue Langevin, France
Materials that display coupled ferromagnetic and ferroelectric orders are of special interest in the field of multiferroics, since they hold clear promise for applications. We present a combined bulk measurement and neutron diffraction study of the insulator Mn
2
GeO
4
which displays a rare phase that hosts spontaneous ferromagnetic and ferroelectric orders that each point along the c-axis. Our experiments show that the magnetism underlying this rich phase is multi-component; a commensurate antiferromagnetic order that is weakly ferromagnetic co-exists with an incommensurate spin spiral that generates ferroelectricity. Our experimental data strongly indicate that the two magnetic modulations combine to form a single, more elaborate doubly-modulated structure, and which therefore provides the means for the direct coupling of the bulk properties. A consequence of this is seen in bulk measurements; after cooling into the MF state under simultaneously poling electric and magnetic fields, we can
ICNS 2013 International Conference on Neutron Scattering

demonstrate a flop of the electric polarization upon sweeping the magnetic field applied along the ferromagnetic caxis. This implies the unusual ability to switch the incommensurate spin-spiral handedness with a magnetic field, which we confirm by spherical neutron polarimetry experiments. Our measurements provide exciting evidence that under appropriate experimental conditions, it is possible to both choose and stabilize a specific ferromagnetic ferroelectric monodomain in the sample.
P.183 Enhancement on magnetic ordering by divalent ions doping of (Bi
0.9
M
0.1
)FeO
3
(M=Pb, Ca)
C-P Wu, H Chou, M Bohra, S R Yah, K S Yang, H W Chang, K C Liu and M Y Chiang
National Sun Yat-sen University, Taiwan
The divalent ions doping effect of Pb and Ca in Bi sites of (Bi
0.9
M
0.1
)FeO
3
(M=Pb, Ca; abbreviation as BPbFO and
BCaFO) multiferroics in magnetic ordering is investigated by the Neutron Powder Diffraction (NPD) in Wombat of
ANSTO, Australia and the X-ray photoelectron spectroscopy. NPD patterns of both samples were measured as a function of temperature, in which an obvious AFM peak decreases in intensity with increasing temperature and finally disappear at higher temperature. The Néel temperature T
N of Pb and Ca doped samples are 680 and 708K, respectively, which are much higher than that of the pure BiFeO3, 643K. The present results are different to earlier reports [1-3] that the chemical pressure of Ca ion and the divalent doping may generate oxygen vacancies were observed to decrease the Fe-O-Fe superexchange coupling and T
N in divalent states. The larger ionic radius of Pb 2+
. The XPS data indicates that both Pb and Ca are
seems creating an negative chemical pressure is now compensated by generating oxygen vacancies, V
O
, which is observed as the existing extra XPS peak at 530.71eV.
The V
O
decreases the size of Fe-O octahedral and enhances the T
N
. For BCaFO, the oxygen vacancies is not observable by XPS and the small lattice enhances Fe-O-Fe superexchange coupling strength that finally further enhances T
N
.
[1] G. Catalan, K. Sardar, Phys. Rev. B.79, 212415 (2009).
[2] R. Palai et al., Phys. Rev. B 77, 014110 (2008).
[3] A. G. Gavriliuk et al., Phys. Rev. B 77, 155112 (2008).
ICNS 2013 International Conference on Neutron Scattering