Magnetic and magnetocaloric behaviors of a perovskite/ hausmannite composite

We present here a detailed study on the magnetic and magnetocaloric (MC) behaviors of a perovskite/hausmannite composite material of LYCMO/Mn3O4, where LYCMO (La0.5Y0.1Ca0.4MnO3) is a primary phase of 95 wt %. The analysis of M(T) data indicates a coexistence of ferromagnetic-paramagnetic transitions associated with LYCMO and Mn3O4 at about 56 and 43 K, respectively. Critical-behavior analyses have proved the composite exhibiting a second-order phase transition at magnetic fields H <= 10 kOe, with critical exponents beta= 0.347 and gamma = 1.167 characteristic of 3D-Heisenberg and 3D-Ising ferromagnets, respectively. At higher fields, it tends to exhibit crossover behaviors of first-/second-order transitions. As analyzing the MC effect upon isothermal M(H) data, we have found the maximum magnetic-entropy change of -3.1 J/kg & sdot;K, and the relative refrigerant capacity (RCP) of -150 J/kg for H = 30 kOe, which are higher than those obtained for other oxides in the same temperature and applied-magnetic ranges. With the absence of hysteresis loop and large RCP value, this material can be used in magnetic-cooling devices working at temperatures T = 40-85 K to liquefy nitrogen.