Structural, Magnetic and Magnetocaloric Study of Rare-Earth and Cobalt Co-Doped La_0.8RE_0.2Cr_0.5Co_0.5O₃ (x = 0.2; RE = Nd and Gd) Chromite

Heavy rare earth chromite’s, specifically RCrO₃ (where R represents Ho, Er, Yb, Lu, and Y), are a class of advanced multifunctional materials that demonstrate multiferroicity, which combines ferroelectricity and canted antiferromagnetism. These materials have significant promise for utilization in magnetic refrigeration applications. This work presents structural, magnetic and magnetocaloric effect (MCE) observed in polycrystalline orthochromites La_0.8RE_0.2Cr_0.5Co_0.5O₃ that have been doped with rare-earth and cobalt elements. The materials were synthesized by the sol-gel auto combustion method. XRD pattern reveals that all the samples crystallize in the perovskite phase with an orthorhombic structure (space group Pbnm). The lattice parameter of the powder samples was calculated from the XRD pattern refinement, which showed a decrease in lattice parameter and volume upon rare-earth substitution. This systemic change in the lattice volume is the result of the lanthanide contraction of the ionic radii of rare earth elements. Magnetic measurement shows Paramagnetic (PM) to Canted Antiferromagnetic (CAFM) transition with Néel temperature (T_N) below 300K and paramagnetic Curie-Weiss temperature (θ) undergoing shift towards lower temperature upon RE and Co co-doping. An increase of considerable magnitude in magnetization has been observed in the doped compounds because of the development of ferromagnetic properties. All the doped compounds showed an enhancement in MCE performance compared to the pristine compound. The compound LaCr₀.₅Co_0.5O₃exhibited a maximum change in magnetic entropy of 0.07Jkg^-1K^-1 when subjected to an applied field of 5T. The Nd and Co co-doped La_0.8Nd_0.2Cr_0.5Co_0.5O₃ compound showed the highest magnetic entropy change of 6 Jkg^-1K^-1, whereas the Gd and Co co-doped La_0.8Gd_0.2Cr_0.5Co_0.5O₃ compound showed magnetic entropy change of 4 Jkg^-1K^-1,both under a 5T applied field. Due to the substantial rise in magnetic entropy change, these materials have potential for use in magnetic refrigeration applications at low temperatures.