Magnetocaloric effect in RAl2 (R = Nd, Sm, and Tm): Promising for cryogenic refrigeration close to liquid helium temperature

NdAl2 and TmAl2 single-crystals display Curie temperature (TC) at 76.5 and 6.0 K, which are significantly close to liquid nitrogen and helium (THe) temperatures, respectively. Maximum entropy-change (−ΔSM) for 0–70 kOe are 35.9 and 8.9 J/kg-K at TC with large cooling efficiency 655 and 398 J/kg for TmAl2 and NdAl2, respectively. Adiabatic temperature change at THe for 0–20 kOe is 3.7 K for TmAl2. This is promising for cryogenic refrigeration down to sub-Kelvin temperature using an electromagnet. The −ΔSM for SmAl2 is low (∼0.5 J/kg-K at TC for 0–70 kOe). The direction-dependent anisotropy in thermal and field variations of ΔSM, and a reasonable correlation between ΔSM and magnetoresistance are realized for NdAl2 and TmAl2.

► Large magnetocaloric effect (35.9 J/kg-K at 6 K for 0–70 kOe) in TmAl2.
► Promising for cryogenic refrigeration close to liquid helium temperature.
► A reasonable correlation between magnetocaloric effect and magnetoresistance is realized for NdAl2 and TmAl2.