Papers by Keyword: Cluster Glass

Abstract: Pr0.5Ca0.5Mn0.99Al0.01O3 compound was prepared by standard solid state reaction to study its ac susceptibility at low temperatures. The X-ray powder diffraction patterns show that the compound is single-phase orthorhombic structure. The cusps of charge ordering and the long range AFM order of the “pseudo”-CE type are suppressed with Al dopping in Pr0.5Ca0.5MnO3 compound. ZFC and FC magnetization of this compound bifurcate at Tf. The behavior of ac susceptibility at low temperatures is investigated. The intensity of the real component ' at the freezing temperature Tf is suppressed with the increase of frequency. Tf is linear with the logarithm of the frequency. The normalized slope P = ΔTf/TfΔlog10ω, which is much lower than canonical insulating spin glass systems in which 0.06 ≤ P ≤ 0.08. The intensity of '' at Tf increases with the increase of frequency. The ground state of this sample is cluster glass.

Abstract: A study of the low temperature magnetic state of polycrystalline colossal magnetoresistance perovskite Nd_2/3Ca_1/3MnO₃ has been carried out. The data obtained, such as strongly divergent ZFC and FC static magnetizations and frequency dependent ac susceptibility, are evident of the glassy magnetic state of the system. Well defined maxima Tmax in the in-phase linear ac susceptibility χ curves were observed, indicating a spin-glass transition. Clear frequency dependence of the cusp temperature Tmax was found. The frequency dependence of Tmax was successfully analyzed by the dynamical scaling theory of a three-dimensional spin glass. Slow relaxation process and variety of relaxation times found imply a cluster glass magnetic state of the compound at low temperatures rather than a canonical spin glass state. The cluster glass state, accompanied by the multiple magnetic transitions of Nd_2/3Ca_1/3MnO₃, might exist due to the competing interaction between the FM clusters and the AFM matrix induced by the complex nanophase segregated state of the compound.

Abstract: In this paper, the rare earth cobaltite Nd_0.80Sr_0.20CoO₃ sample was prepared using conventional solid state reaction method. The dc magnetization, ac susceptibility, hysteresis loop of polycrystalline Nd_0.80Sr_0.20CoO₃ sample was carried out using the physical properties measurement system of Quantum Design. A dynamic analysis of ac susceptibility implies cluster glass transition temperature T_SG =72.06 K which occurs much higher by 25 K than that point at which the dc magnetization reaches a maximum. The cluster glass behavior of polycrystalline Nd_0.80Sr_0.20CoO₃ sample, which originates from the phase separation at low temperature, was systematically investigated in this paper. It was found that the sample has a small spontaneous magnetization and the weak frequency dependent peak so that we assume that the sample is cluster-glass.