Magnetic properties and magnetocaloric effect of the Cr-based spinel sulfides Co_1-xCu_xCr₂S₄

Crystallographic structure, magnetic properties, and magnetic entropy change of the Cr-based spinel sulfides Co_1-xCu_xCr₂S₄ (x=0-0.8) have been investigated. All these compounds crystallize into the cubic spinel structure, the Cu substitution shrinks linearly the lattice constant at a ratio of 0.0223 Å per Cu atom in the unit cell, and enhances linearly the Curie temperature and the spontaneous magnetization at the rates of 18 K and 0.33 μ_B/f.u. per Cu atom in the unit cell, respectively. All these compounds show a typical behavior of second order magnetic transition, and a room temperature magnetic entropy change of 2.57 J/kg·K is achieved for Co_0.4Cu_0.6Cr₂S₄.