Metamagnetic Transition and Magnetic Phase Diagram of TmGa Alloy

TmGa alloy was prepared by arc melting. TmGa exhibited two successive magnetic transitions at temperatures, T_AF=11.5 K antiferromagnetic (AFM_Ι) to AFM_Π and T_N=15 K AFM_Π to paramagnetic (PM). A field-induced metamagnetic transition AFM-FM states was observed. Although the ground state remained AFM for TmGa, the ferromagnetic (FM) state could be induced by a magnetic field at about 12 K under relatively low field change of 0.02 T. So the transitions AFM_Ι-FM, FM-AFM_П and AFM_П-PM were observed in a certain magnetic field, and the AFM_Π state completely disappeared under 0.2 T. The transition from low temperature AFM state (AFM_I) to FM state induced by a magnetic field was irreversible. On the contrary, the transition from high temperature AFM state (AFM_II) to FM state was reversible. A magnetic phase diagram was made based on the magnetic measurement. Additionally, TmGa compound exhibited an excellent magnetocaloric effect (MCE) around transition temperature. Under field change of 5 T, the maximum values of magnetic entropy change -ΔS_M was 34.2 J·kg^-1·K^-1. It was worth noting that under field changes of 1 and 2 T, the maximum values of -ΔS_M were 12.9 and 20.7 J·kg^-1·K^-1, meanwhile, large values of refrigerant capacity (RC) (69, 149 and 364 J·kg^-1) were observed, respectively. It was expected to have effective applications in low temperature magnetic refrigeration.