Observation of superior magnetocaloric properties near ambient temperature in (La-Ce-Pr-Nd)10Fe90-xBx ribbons

In this study, ribbons with a nominal composition of MM₁₀Fe_90-xB_x (where MM denotes mischmetal La-Ce-Pr-Nd derived from Bayan obo ore of China without a separation process) were fabricated using the melt-spinning method. The structural and magnetocaloric properties were systematically investigated by means of X-ray diffraction, scanning electron microscopy, transmission electron microscopy, differential scanning calorimetry and vibrating sample magnetometry. The results indicate that crystalline phase formation in the ribbons is significantly suppressed with increasing B content. The Curie temperature increases from 269 K for x = 2 to 345 K for x = 6, covering the room-temperature range. The ribbons show a superior magnetocaloric effect and relative cooling power (RCP) near room temperature except for x = 2. With a magnetic field change of 3 T, the ribbon with x = 5 exhibits a maximum isothermal entropy change of $-\mathrm{\Delta }{S}_{T,\max }$$-\mathrm{\Delta }{S}_{T,\max }$ = 2.42 Jkg⁻¹K⁻¹ and a corresponding RCP of 300 Jkg^-1. The Landau model was applied to interpret the phase transition and magnetocaloric effect in the ribbons. The present study provides useful scientific insights for developing applicable magnetic refrigerants near room temperature.