Structure, magnetic and cryogenic magneto-caloric properties in intermetallic gallium compounds RE2Co2Ga (RE = Dy, Ho, Er, and Tm).

The intermetallic gallium compounds RE₂Co₂Ga with different rare earths (RE = Dy, Ho, Er, and Tm) were synthesized, and their crystal structure, microstructure, magnetic, and cryogenic magneto-caloric performances were investigated. The RE₂Co₂Ga compounds crystallize with an ordered orthorhombic W₂B₂Co-type structure (space group Immm). All the RE₂Co₂Ga compounds undergo ferromagnetic (FM) ordering (second-order) from a paramagnetic to FM transition which induces reversible magneto-caloric effects (MCE). The Curie temperatures (T_C) in RE₂Co₂Ga compounds are determined to be 55.0, 38.5, 25.5, and 11.6 K for RE = Dy, Ho, Er, and Tm, respectively, which fulfill the de Gennes scaling. The RE₂Co₂Ga compounds show relatively small MCE (i.e., −ΔS_M, isothermal magnetic entropy change) around their own phase transition temperatures, and the maximal values of −ΔS_M are 7.5, 14.6, 11.2, and 13.2 J/kg K in the field change (ΔH) of 7 T for RE = Dy, Ho, Er, and Tm, respectively. Accordingly, the values of the relative cooling power are 212, 335, 304, and 239 J/kg, respectively. [ABSTRACT FROM AUTHOR]