Wanfa Liu

Temperature- and magnetic-field-induced magnetization reversal in perovskite YFe0.5Cr0.5O3

Perovskite YFe0.5Cr0.5O3 exhibits magnetization reversal at low applied fields due to the competition between the single ion magnetic anisotropy and the antisymmetric Dzyaloshinsky–Moriya interaction. Below a compensation temperature (Tcomp), a tunable bipolar switching of magnetization is demonstrated by changing the magnitude of the field while keeping it in the same direction. The present compound also displays both normal and inverse magnetocaloric effects above and below 260 K, respectively. These phenomena coexisting in a single magnetic system can be tuned in a predictable manner and have potential applications in electromagnetic devices.

Large reversible magnetocaloric effect in HoTiO3 single crystal

Large magnetocaloric effect has been observed in perovskite-type HoTiO3 single crystal accompanied by a second-order magnetic phase transition at TC ≈ 53 K. The values of maximum magnetic entropy change are about 5.96 and 11.56 J kg−1 K−1 under the magnetic field change of 2 and 5 T, respectively, without any detectable thermal and magnetic hysteresis loss. The large magnetic entropy change is attributed to the sharp magnetization jump, related to anomalies of the lattice parameters just at the Curie temperature. Such a large reversible magnetocaloric effect makes the perovskite HoTiO3 attractive for pursuing new materials for magnetic refrigeration.

Evidence of two distinct dynamical freezing processes in single-layered perovskite La0.7Sr1.3CoO4

The static and dynamic features of magnetization have been investigated in terms of dc magnetization, ac susceptibility, and memory effects on single-layered perovskite La(0.7)Sr(1.3)CoO(4). The results indicate that short-range ferromagnetic clusters coexist with the glassy magnetic state, i.e., a cluster-glass phase between T(f) and T(G) and a spin-glass-like phase below T(f). The clear evidence of memory effects in the dc magnetization is also observed below T(f) and T(G), respectively. These two glassy states with cooperative relaxation processes may derive from the different interaction processes among nanoscale ferromagnetic clusters mediated by the matrix, which is influenced by changing the spin state of Co(3+) ions in spontaneously phase-separated cobaltite.

Magnetocaloric properties of single crystalline YbTiO3 with second order phase transition

Magnetic entropy change and refrigerant capacity in applied magnetic fields up to 5 T have been investigated for the single crystalline YbTiO3. The maximal magnetic entropy changes at the second order magnetic phase transition temperature TC (42 K) are about 2.47 and 5.25 J kg?1 K?1 under 1.5 and 5 T, respectively. The magnetic entropy change is attributed to the sharp magnetization jump, related with anomalies of the lattice parameters just at the Curie temperature. The magnetic entropy change for YbTiO3 can be well described by a phenomenological universal curve behavior. The field dependence of the magnetic entropy change and the relative cooling power was also studied. From the analysis of the relationship between the local exponent n and the critical exponents, we conclude that the critical behavior of YbTiO3 belongs to the three-dimensional Heisenberg class, which was also confirmed by the heat capacity measurement.