Magnetic Properties of Single Layered Cobaltite
Sr1.5La0.5CoO4 Thin Film
Pankaj K. Pandey *, D. M. Phase and R. J. Choudhary
UGC DAE Consortium for Scientific Research, Indore 452001, India
* Presenting author e-mail: pankaj@csr.res.in
Abstract: Using pulsed laser deposition, we have synthesized highly textured thin films of Sr1.5La0.5CoO4 on LaAlO3
(001) substrate. The dc-magnetization (M vs. T) measurements divulge ferro to para magnetic transition at ~ 140 K. Inverse
susceptibility (1/χ) nicely demonstrates aspects of Griffith phase. Coercivity variation with T1/2 suggests interparticle
interactions in the sample. M vs. T reveal bifurcation between zero-field cooled (ZFC) and field cooled data as well as a
cusp in the ZFC data. Our analysis indicates that the thermo-magnetic irreversibility and cusp in ZFC magnetization are
because of the anisotropic ferromagnetic state. The isothermal time dependence of the magnetization discloses the existence
of multiple metastable states in the system. Interestingly, we find spin glass like slow relaxation of magnetization and aging
effect which are found to be described by hierarchical model of spin glasses.
20
(008)
(004)
(002)
Intensity (Arb. Units)
(006)
3. FIGURES AND IMAGES
1. INTRODUCTION
40
60
degree
Figure 1: XRD pattern showing highly oriented
nature of the grown film along c-direction
1/e/emu)
7
 ZFC
 FC
'FC
-7
2.0x10
 (emu/Oe)
Recently, a renewed interest has occurred in layer
structured cobalt oxide based two-dimensional (2D)
compound. Earlier report confirmed that the CoO 2layers can act as a stage for a two-dimensional
ferromagnetism as well as superconductivity in
layered cobaltates.1 In particular, the two dimensional
layered compound Sr2CoO4 (SCO) has been reported
to possess metallicity, ferromagnetism and spin-lattice
coupling.1-2 Interestingly, partial replacement of Sr by
rare-earth elements manifest a wealth of intriguing
magnetic properties. Sr1.5La0.5CoO4 and SrPrCoO4;
which exhibit phase separation upholds FM ground
state of SCO whereas Sr1.5Pr0.5CoO4, SrLaCoO4, and
Sr1.25Nd0.75CoO4 are reported to exhibit spin-glass
state.3 Here, we optimized the growth condition and
synthesized highly oriented thin film of Sr1.5Lr0.5CoO4
and present its magnetic properties.
1/
Curie-Weiss fitting
6.0x10
7
4.0x10
Happ = 200 Oe
7
2.0x10
H = 500 Oe
50
-7
1.0x10
100
150
200
Temperature (K)
0.0
0
50
100
150
200
Temperature (K)
Figure 2: χ vs. T curve along with calculated χ'FC at
500 Oe. Inset shows 1/χ vs. T behavior.
tw =30 min
0.999
tw = 1 hour
FC in 100 Oe
Coercivity (kOe)
We have synthesized highly textured thin film of
Sr1.5La0.5CoO4 on LaAlO3 (001) substrate as shown in
Fig 1. The temperature dependence of the ZFC and
FC magnetization reveals history dependence with a
bifurcation between ZFC and FC data at an
irreversibility temperature Tirr. Tirr temperature is
higher than the temperature at which peak appears in
ZFC data. Approach suggested by Joy et al.4 (as
shown in Fig.2) imply that ZFC magnetization is
nothing but the FC magnetization modified by
coercive field. As shown in the inset of Fig.2, 1/χ
behavior shows downturn above TC which is one of
the characteristics of Griffith phase. Fig.3 illustrates
thermo remnant magnetization at 10 K for different
wait time (tw) before to record the data. Coercivity
variation with T1/2 suggests interparticle interactions
in the sample which further confirmed by Wohlfarth
relation (not shown).5
The Isothermal time dependence of the magnetization
discloses the presence of metastability in the system.
Interestingly, we find spin glass like slow relaxation
of magnetization and aging effect which are attributed
to the combined effect of broad distribution of
relaxation time and inter-particle interactions.
M (t) / M(0)
2. RESULTS AND DISCUSSION
10
0.996
5
0
2
4
6
8
10
T 1/2 (K 1/2)
0.993
0
2000
Time (sec)
4000
Figure 3: Wait time dependence of TRM at T= 10K .
Inset shows coercivity vs. T1/2.
REFERENCES
[1] Matsuno et al, Phys. Rev. Lett. 93,167202 (2004).
[2] Pankaj K. Pandey et al, Appl. Phys. Lett. 102,
142401 (2013).
[3] R. Ang et al, Appl. Phys. Lett. 92, 162508 (2008),
and references therein.
[4]. P. A. Joy et al, J. Phys.: Condens. Matter 10,
11049 (1998).
[5] A. K. Pramanik and A. Banerjee phys. Rev. B 82,
094402 (2010).