Disordered Structure with CaCu5 Type and Uniaxial Magneto-Crystalline Anisotropy Induced by High Entropized Cocktail Effect in Sm2Co17 Based Intermetallics

Abstract

A series of Sm₂Co₁₇ based high entropized intermetallic compounds with structural formula of (Sm_1/n……Rn_1/n)₂(Fe_1/3Co_1/3Ni_1/3)₁₇ (R=Y, La, Ce, Pr, Nd) are designed by random occupations of equiatomic ratios of light rare earths at Sm site and 3d transition metals at Co site. These high entropized samples are verified theoretically and experimentally to be single-phase by thermodynamic theory of high entropy (ΔS＞20.06R) and the powder X-ray diffraction, respectively. Based on Rietveld structural refinement, the structural model is preferred to be a disordered hexagonal CaCu₅ type structure, where the rare earths and 3d transition metals co-occupy randomly 1a site. The high entropized cocktail effect not only causes uniaxial anisotropy, but also modulates the saturation moment M_s and anisotropic field H_A. The contribution to magnetic moment of valence state for Ce is studied with a magnetic valence model.