Giant low-field magnetocaloric effect in unstable antiferromagnetic Tm_1–xEr_xNi₂Si₂ (x = 0.2, 0.4) compounds

Magnetic refrigeration (MR) technology is regarded as an ideal solution for cryogenic applications, relying on magnetocaloric materials which provide necessary chilling effect. A series of polycrystalline Tm_1–xEr_xNi₂Si₂ (x = 0.2, 0.4) compounds was synthesized, and their magnetic properties, magnetic phase transition together with magnetocaloric effect (MCE) were studied. The Tm_1–xEr_xNi₂Si₂ (x = 0.2, 0.4) compounds display a field-induced metamagnetic transition from antiferromagnetic (AFM) to ferromagnetism (FM) in excess of 0.2 T, respectively. Meanwhile, the AFM ground state is unstable. Under the field change of 0–2 T, the values of maximal magnetic entropy change (−ΔS_M^max) and refrigerant capacity (RC) for Tm_0.8Er_0.2Ni₂Si₂ compound are 17.9 J/(kg·K) and 83.5 J/kg, respectively. The large reversible MCE under low magnetic fields (≤2 T) indicates that Tm_0.8Er_0.2Ni₂Si₂ compound can serve as potential candidate materials for cryogenic magnetic refrigeration.