Effects of Mn substitution on crystal structure, magnetic and magnetocaloric properties of (Co1−xMnx)2B compounds

Abstract

The crystal structure, magnetic and magnetocaloric properties of (Co1−xMnx)2B (x = 0.0, 0.1, 0.2, 0.25, 0.3, 0.35, 0.40) compounds were investigated by x-ray powder diffraction (XRD) and magnetization measurements. All compounds crystallize in a body-centred tetragonal single phase with the CuAl2-type structure. Due to the changes of lattice stability and ferromagnetic–antiferromagnetic exchange coupling interaction, the room temperature magnetization and the Curie temperature (TC) of (Co1−xMnx)2B compounds first increases at about x = 0.1 and then decreases with the substitution of Mn for Co. Second-order phase transition was confirmed based on the isothermal magnetization curves and the isothermal entropy change (ΔSM) was determined for the samples with x = 0.3, 0.35 and 0.4. The maximal magnetic entropy (|ΔSM|) under a field change from 0 to 5 T are found to be 2.49, 2.37 and 2.02 J kg−1·K for x = 0.3, 0.35 and 0.4, respectively. The corresponding relative cooling powers (RCP) are evaluated to be 59.74, 78.94 and 113.50 J kg−1. Given the low cost of Co, Mn and B, (Co1−xMnx)2B compounds may come as an base compound for a more efficient magnetocaloric material.