Effect of partial substitution of Cr 3+ for Fe 3+ on magnetism, magnetocaloric effect and transport properties of Ba 2FeMoO 6 double perovskites

Abstract

Magnetism, magnetocaloric effect and transport properties of Cr doped double perovskites compound Ba 2Fe 1− x Cr x MoO 6 with (0 ≤ x ≤ 1) were investigated by magnetization and electrical resistivity measurements. The samples show a cubic structure of cell parameter, a, decreases with increasing Cr content. The temperature variation in magnetization reveals a ferromagnetism for all samples with T C decreases significantly as the Cr doping content increases from 340 K to 310 K for x = 0 and 1, respectively. The saturation magnetic moment, μ S, was found to decrease with increasing the Cr doped content from 3.63 μ B/f.u. for x = 0 to 2.69 μ B/f.u. for x = 1 which may relate to the increase of the anti-site disorder defects or magnetic dilution due to the substitution of Cr for Fe. The magnetocaloric effect is calculated from the measurement of initial isothermal magnetization versus magnetic field at various temperatures. The maximum magnetic entropy change, Δ S M max , of Cr doped double perovskite is found to decrease with increasing of Cr content from 2.08 J/kg K for x = 0 to 0.55 J/kg K for x = 1 upon 1 T applied field change. Interestingly, the value of Δ S M max = 2.08 J / kg K for x = 0 at 1 T was found to be about 64% that of pure Gd, which is thought to be the optimum magnetic refrigerant for use near room temperature. Thus, this perovskite is beneficial for the household application of active magnetic refrigerant materials. The zero field electrical resistivity measurements exhibit a change from metallic behavior at x = 0 to semiconducting like behavior for all doped samples ( x ≥ 0.2) over the entire measurement temperature region from 4.2 K to 300 K.