Structural, magnetic and magnetocaloric properties of nickel-copper ferrite with chromium substitution

The structural, magnetic and magnetocaloric properties of Ni0.6Cu0.4Fe1.5Cr0.5O4 sample have been investigated. The sample was synthesized by sol-gel method. The X-ray diffraction result indicates that the ferrite sample has a cubic spinel type structure (Fd3̅m space group). Magnetization versus temperature showed that sample exhibits a second-order paramagnetic (PM) -ferromagnetic (FM) phase transitions with Curie temperature TC equal to 660 K. Magnetocaloric properties were obtained by measuring a family of M(H, T) curves near TC and calculating both magnetic entropy change (ΔSM) and relative cooling power (RCP). The magnetic entropy change reaches a maximum value |∆SM max| of about 1.39 J.K-1 .kg -1 for μ0H= 5 T corresponding to relative cooling power (RCP) of 142 J.kg-1 . These values are comparable to that of some other ferrite materials considered as possible candidates for magnetic refrigeration.