Structure and Magnetic Property of High‐Entropy Intermetallics Based on SmCo₅ with the Equiatomic Ratios at Sm and Co Sites

Abstract

SmCo5‐based high‐entropy intermetallic compounds (Sm1/3Pr1/3Nd1/3)(Co1/3Ni1/3 Cu1/3)5 and (Sm1/4Ce1/4Pr1/4Nd1/4)(Co1/3Ni1/3Cu1/3)5 are prepared by substituting equiatomic ratios of rare earths at the Sm site and 3d transition metals at the Co site, respectively. Their crystal structures, chemical compositions, and magnetic properties are investigated. X‐ray diffraction confirms that the two high‐entropy intermetallic compounds are single phase with hexagonal CaCu5‐type structure. The configuration entropies are 6.59R for (Sm1/3Pr1/3Nd1/3)(Co1/3Ni1/3Cu1/3)5 and 6.88R for (Sm1/4Ce1/4Pr1/4Nd1/4)(Co1/3Ni1/3Cu1/3)5, respectively. Both of them show spin‐glass and field‐induced ferromagnetic order due to the disordered ferromagnetic state induced by the site‐disordered spin interactions at low temperature and the ordered arrangement of moments driven by the external field at the ferromagnetic transition temperature. Abnormal magnetic hysteresis loops are observed at the spin‐glass order temperature, which is suggested to be associated with the anisotropy induced by the interaction coupling between the 4f rare earth and the 3d transition metal.

High entropy induced structural stabilization, anisotropy transition and magnetization enhancement effect in La2Co17

“…16 SmCo 5based HEICs have been studied systematically, where the maximum energy product and Vickers hardness of (Sm 1/3 Pr 1/3 Y 1/3 )Co 5 and (Sm 1/4 Pr 1/4 Nd 1/4 Y 1/4 )Co 5 are enhanced by doping Y, 17 and the spin glass and field-induced ferromagnetic transition are observed in (Sm 1/3 Pr 1/3 Nd 1/3 )(Co 1/3 Cu 1/3 Ni 1/3 ) 5 and (Sm 1/4 Ce 1/4 Pr 1/4 Nd 1/4 )(Co 1/3 Cu 1/3 Ni 1/3 ) 5 , which is suggested to be due to the mixture of multiple rare earth elements at the Sm site and Co, Cu, and Ni at the Co site. 18 Compared with the RCo 5 intermetallic compound, the R 2 Co 17 intermetallic compound has a high saturation magnetic moment and Curie temperature but a low coercivity. [19][20][21][22] Although La 2 Co 17 does not exist naturally, the La 2 Co 17 phase can be stabilized via the substitution of a non-magnetic element for Co; [23][24][25][26][27] however, its magnetization can be weakened and causes a decrease in the Curie temperature due to the magnetic diluting effect induced by substituting a non-magnetic element for the strongly magnetic Co.…”