Structural stability, magnetic properties and hardness of equiatomic light rare earth-cobalt with CaCu5 type structure before and after adding Y

Abstract To explore the existence of single-phase high entropy intermetallic compound (HEIC) by elements randomly occupation at one sublattice, the four intermetallic compounds (Sm1/2Pr1/2)Co5, (Sm1/3Pr1/3Y1/3)Co5 (Sm1/3Pr1/3Nd1/3)Co5 and (Sm1/4Pr1/4Nd1/4Y1/4)Co5 have been synthesized by vacuum arc-melting technology, and their crystal structures, microstructures, magnetic properties, and hardness have been systematically studied. X-ray diffraction confirms that the four intermetallics are single phase with hexagonal CaCu5 type structure. A configuration entropy of 11.56 ​J/(mol·K) is obtained in (Sm1/4Pr1/4Nd1/4Y1/4)Co5. The morphologic images show that grains are refined via adding Y into (Sm1/2Pr1/2)Co5 and (Sm1/3Pr1/3Nd1/3)Co5. These intermetallics are ferromagnetic characteristics and show strong magnetocrystalline anisotropy along c axis at room temperature. Y doping into (Sm1/2Pr1/2)Co5 and (Sm1/3Pr1/3Nd1/3)Co5 induces the enhancements of anisotropy field, maximum energy product and Vickers hardness. The improvements of magnetic properties and hardness might be due to the modulation of lattice parameter ratio (c/a) by yttrium doping.