Coexistence of interacting ferromagnetic clusters and small antiferromagnetic clusters in La_0.5Ba_0.5CoO₃

Abstract

We report detailed dc magnetization and linear and nonlinear ac susceptibility measurements on the hole doped disordered cobaltite La0.5Ba0.5CoO3. Our results show that the magnetically ordered state of the system consists of coexisting non-ferromagnetic phases along with percolating ferromagnetic clusters. The percolating ferromagnetic clusters possibly start a magnetic ordering at the Curie temperature of 201.5(5) K. The non-ferromagnetic phases mainly consist of antiferromagnetic clusters with size smaller than the ferromagnetic clusters. Below the Curie temperature the system exhibits an irreversibility in the field cooled and zero field cooled magnetization and a frequency dependence in the peak of ac susceptibility. These dynamical features indicate the possible coexistence of spin-glass phase along with ferromagnetic clusters similar to La(1-x)Sr(x)CoO3 (x ≥ 0.18), but the absence of field divergence in the third harmonic of ac susceptibility and zero field cooled memory clearly rule out any such possibility. We argue that the spin-glass phase in La(1-x)Sr(x)CoO3 (x ≥ 0.18) is associated with the presence of incommensurate antiferromagnetic ordering in non-ferromagnetic phases, which is absent in La0.5Ba0.5CoO3. Our analysis shows that the observed dynamical features in La0.5Ba0.5CoO3 may be due to progressive thermal blocking of ferromagnetic clusters, which is further confirmed by Wohlfarth's model of superparamagnetism. The frequency dependence of the peak of ac susceptibility obeys the Vogel-Fulcher law with τ0 ≈ 10(-9) s. This together with the existence of an AT-line in H-T space indicates the presence of significant inter-cluster interaction among these ferromagnetic clusters.

Magnetic percolation and inequivalence of Fe sites in YFe x Co2−x (x = 0.03 and 1) Laves phase compounds

“…This is in accordance with the presented results as the frequency dependence of v(T) was observed as an indication of dynamic processes in YFe 0.03 Co 1.97 . At low fields and below peak temperature, the FC magnetization should be constant with temperature for canonical spin-glass [10]. It is not the case in present investigation, as the magnetization value is decreasing slightly at low temperatures.…”

Synthesis, Structural and Magnetic Properties of La0.5Ba0.5CoO2.75+x

“…3(b). Also, we cannot determine the spin orientation by neutron powder diffraction (Table 4 1 (x = 0.25) [18]. In case of x = 0.16, a short-range ordered AFM state, which cannot be detected by NPD, may coexist with the long-range ordered FM state at low temperature as well.…”

Magnetic Properties and Phase Diagram of Ni50Mn $$_{50-x}$$ 50 - x Ga $$_{x/2}$$ x / 2 In $$_{x/2}$$ x / 2 Magnetic Shape Memory Alloys

“…A linear relationship [18], and a value of zv in the range of 4-12 is typical for the case of a spin-glass system [35,36]. However, the value of s à is very small compared to those between 10 À12 and 10 À14 reported for conventional metallic spin-glass systems [35,36], suggesting a very weak interaction similar to the case of La 0:5 Ba 0:5 CoO 3 [37].…”