Giant magnetocaloric effect in HoGa compound over a large temperature span

Abstract

We have studied experimentally the magnetic properties and magnetocaloric effect (MCE) in HoGa compound. Two subsequent magnetic transitions, a spin-reorientation (SR) transition followed by a ferromagnetic (FM)–paramagnetic (PM) transition, are observed at T S R ∼ 20 K and T C ∼ 69 K , respectively. Both transitions contribute greatly to the magnetic entropy change ( Δ S M ) , each yielding a significant peak on their Δ S M – T curve. A considerable value of refrigerant capacity (RC) is obtained in HoGa, due to the large MCE over a wide temperature span. For a magnetic field change of 0–5 T, the maximal values of − Δ S M are 17.1 J/kg K and 7.8 J/kg K at T C and T S R , respectively, and the RC reaches its maximal value of 455 J/kg in an optimal reversible refrigerant cycle with cold and hot sinks at T cold ∼ 16 K and T hot ∼ 99 K . Large reversible MCE and the giant value of RC indicate the potentiality of HoGa as a candidate magnetic refrigerant for nitrogen liquefaction.