Magnetic properties and magnetocaloric effect in RE₅₅Co₃₀Al₁₀Si₅ (RE = Er and Tm) amorphous ribbons

The magnetic and magnetocaloric effects (MCE) of the amorphous RE_55Co_30Al_10Si_5 (RE=\rm Er and Tm) ribbons were systematically investigated in this paper. Compounds with R =\rm Er and Tm undergo a second-order magnetic phase transition from ferromagnetic (FM) to paramagnetic (PM) around Curie temperature T_\rm C \sim 9.3 K and 3 K, respectively. For Er_55Co_30Al_10Si_5 compound, an obvious magnetic hysteresis and thermal hysteresis were observed at low field below 6 K, possibly due to spin-glass behavior. Under the field change of 0 T-5 T, the maximum values of magnetic entropy change (-\Delta S_\rm M^\rm max) reach as high as 15.6 J/kg\cdotK and 15.7 J/kg\cdotK for Er_55Co_30Al_10Si_5 and Tm_55Co_30Al_10Si_5 compounds, corresponding refrigerant capacity (RC) values are estimated as 303 J/kg and 189 J/kg, respectively. The large MCE makes amorphous RE_55Co_30Al_10Si_5 (RE=\rm Er and Tm) alloys become very attractive magnetic refrigeration materials in the low-temperature region.