Spin-glass-like dynamics of ferromagnetic clusters in La_0.75Ba_0.25CoO₃

Abstract

We report the magnetization study of the compound La0.75Ba0.25CoO3 where Ba 2+ doping is just above the critical limit for percolation of ferromagnetic clusters. The field cooled (FC) and zero field cooled (ZFC) magnetization exhibit a thermomagnetic irreversibility and the ac susceptibility show a frequency dependent peak at the ferromagnetic ordering temperature (TC ≈203 K) of the clusters. These features indicate about the presence of a non-equilibrium state below TC . In the nonequilibrium state, the dynamic scaling of the imaginary part of ac susceptibility and the static scaling of the nonlinear susceptibility clearly establish a spin-glass like cooperative freezing of ferromagnetic clusters at 200.9(2) K. The existence of spin-glass like freezing of ferromagnetic clusters is further substantiated by the ZFC aging and memory experiments. We also observe certain dynamical features which are not present in a typical spin-glass, such as, initial magnetization after ZFC aging first increases and then decreases with the wait time and an imperfect recovery of relaxation in negative temperature cycling experiments. This imperfect recovery transforms to perfect recovery on concurrent field cycling. Our analysis suggests that these additional dynamical features have their origin in inter-cluster exchange interaction and cluster size distribution. The inter-cluster exchange interaction above the magnetic percolation gives a superferromagnetic state in some granular thin films but our results show the absence of typical superferromagnetic like state in La0.75Ba0.25CoO3.

Magnetic ordering of the martensite phase in Ni–Co–Mn–Sn-based ferromagnetic shape memory alloys

“…However, it is critically important to ensure the true identity of these nanometric clusters in the first place. In case of spin clusters, (i) size should decrease with increasing temperature as temperature is expected to weaken inter-A c c e p t e d M a n u s c r i p t cluster interaction; and (ii) they should cease to exist beyond Tf [30][31][32]. But, SANS analysis in our case reveals quite the opposite.…”

“…One particularly striking observation in their study is the growing size of the spin clusters with increasing temperature. This contradicts the widely accepted view that spin clusters shrink with increasing temperature, as thermal energy weakens inter spin interactions [30][31][32]. In fact, this brings us to the following two important points: (i) it is important to eliminate the possibility of occurrence of nanometric structural clusters during such SANS analysis; (ii) it is prudent to combine SANS analysis with AC susceptibility measurement in order to conclusively identify the nature of the clusters.…”

An important role of temperature dependent scattering time in understanding the high temperature thermoelectric behavior of strongly correlated system: La0.75Ba0.25CoO3

“…33 The step-by-step synthesis details of barium doped LaCoO 3 compounds are provided in the earlier work by Devendra et al 26,27 For Seebeck coefficient measurement, the synthesized powder sample was pelletized under the pressure of ∼35 Kg/cm 2 . Further, it was sintered at 1100 0 C for 12 hours.…”

“…Transport and magnetic properties of barium doped LaCoO 3 compound has been studied by several authors. [25][26][27][28][29][30] Mandal et al have studied the temperature dependent Seebeck coefficient of this compound up to 335 K. To the best of our knowledge, the high temperature thermopower behavior of La0.75Ba0.25CoO3 compound has not been explored so far. Also, the detailed study of TE properties of this compound using electronic band structure is still lacking in the literature.…”

Understanding the High Temperature Thermoelectric Properties of La$_{0.82}$Ba$_{0.18}$CoO$_{3}$ Compound using DFT+U Method

“…23 Synthesis of the present sample under study is similar to the earlier synthesized compounds, where different amount of barium doping at lanthanum site of LaCoO 3 have been done. The detailed synthesis information are provided in the previous work carried out by Devendra et al 24,25 The as-prepared powders were calcined at 1125 0 C for 12 h. To perform the α and σ measurements, the powders were further pelletized under the pressure of ∼35 kg/cm 2 and sintered at 1125 0 C for 12 h. α measurement were carried out on the pellet having the diameter and thickness ∼5 mm and ∼0.5 mm, respectively. The resistivity measurement were performed on the rectangular bar shaped sample with dimensions of ∼5 mm length, ∼1 mm width and ∼0.5 mm thickness by using four-probe method.…”