Magnetocaloric effect and critical behavior of Ni1−xMnxCr2O4 (x = 0, 0.10, and 0.50) compounds

Abstract

Single-phase polycrystalline samples of Ni1−xMnxCr2O4 (x = 0.0, 0.10, and 0.50) were prepared by the sol–gel route, and their structural, magnetic, and magnetocaloric properties and critical behavior were studied. Structural transformation from a tetragonal (I41/amd) to a cubic (Fd3¯m) phase is observed at room temperature due to the substitution of Jahn–Teller inactive Mn2+ ions. Mn substitution gives rise to a reduction in ferrimagnetic transition temperature. A significant increase in magnetic entropy change (−ΔSM) and relative cooling power (RCP) is observed upon Mn substitution. For x = 0.50, the estimated value of −ΔSM = 2.9 J kg−1 K−1 and the relative of cooling power RCP = 58.2 J kg−1 for an applied field of H = 9 T. The ferrimagnetic transition is studied by recording isothermal magnetization data in a close temperature interval in the vicinity of the transition for the maximum applied field up to 9 T. These data were analyzed based on a modified Arrot plot method. The estimated values of critical exponents do not fall under any specific critical state model and they are discussed in detail.