Magnetic Properties and Magnetocaloric Effect (MCE) in the Spinel ACr2O4 (A = Co, Ni) Oxides.

The multiferroic spinel crystalline ACr2O4(A = Co, Ni) were synthesized via a traditional sol-gel reaction and characterized with respect to the structural, magnetic properties and magnetocaloric performances. The ACr2O4 oxides are confirmed to crystallize in cubic Al2MgO4-type structure with space group Fd 3 ¯ m and tetragonal CdMn2O4-type structure with I41/amdz space group for A = Co, Ni, respectively. Both ACr2O4 compounds reveal a typical second-ordered magnetic transition (SOMT) form paramagnetic to ferromagnetic (PM-FM) around its own Curie temperature TC and followed by a low temperature anomalous which is probably due to the spin glass (SG) transition behavior. The calculated peak values of magnetic entropy change (− ∆SMmax) around its own TC under the external magnetic field changes ΔH = 7 T are 1.54 and 1.19 J·kg−1 K−1 for A = Co, Ni, respectively, and the corresponding relative cooling power (RCP) is 22.2 and 22.33 J·kg−1. [ABSTRACT FROM AUTHOR]