Structural, magnetic and magnetocaloric properties in RE₂Ni_1.5Ga_2.5 (RE = Dy, Ho, Er and Tm) compounds

The crystal structure together with the magnetic and magnetocaloric properties in RE₂Ni_1.5Ga_2.5 (RE = Dy, Ho, Er and Tm) have been investigated systematically. All the RE₂Ni_1.5Ga_2.5 compounds crystallize in a CaIn₂-type structure of (P63/mmc space group). A second-ordered magnetic phase transition (SOPT) from ferromagnetic to paramagnetic (FM to PM) is occurred in RE₂Ni_1.5Ga_2.5 compounds with the Curie temperatures (T_C) of approximately 16.1, 10.6, 4.1 and below 2 K for RE of Dy, Ho, Er and Tm, respectively. The magnetocaloric parameters including magnetic isothermal entropy change/temperature-averaged magnetic entropy change -ΔS_M^max/TEC (5) and relative cooling power RCP are calculated with the values of 10.01/9.92 J/kg K and 418.6 J/kg for Dy₂Ni_1.5Ga_2.5, 20.12/19.65 J/kg K and 644.1 J/kg for Ho₂Ni_1.5Ga_2.5, 18.07/17.69 J/kg K and 447.1 J/kg for Er₂Ni_1.5Ga_2.5, as well as 18.22/16.75 J/kg K and 330.7 J/kg for Tm₂Ni_1.5Ga_2.5 with magnetic field change (ΔH) of 0–7 T, respectively. Notably, Ho₂Ni_1.5Ga_2.5 exhibits ralatively high magnetocaloric parameters, which suggests that Ho₂Ni_1.5Ga_2.5 is a competitive candidate among the MCE materials in the field of cryogenic magnetic refrigeration (MR).