Large reversible cryogenic magnetocaloric effect in rare earth iron carbides of composition RE2FeC4 (RE=Ho, Er, and Tm)

At cryogenic temperatures, the investigations of magnetic phase transition and magnetocaloric effect in RE2FeC4 (RE = Ho, Er, and Tm) compounds were performed. Ho2FeC4 and Er2FeC4 compounds undergo two magnetic phase transitions with the temperature decreasing: from paramagnetic (PM) to ferromagnetic (FM) transition at their respective Curie temperature (TC) and from FM to antiferromagnetic (AFM) or ferrimagnetic (FIM) transition below 2 K Tm2FeC4 compound exhibits only a second-order PM to FM phase transition at TC = 6 K. Large reversible MCE without hysteresis loss is observed in RE2FeC4 (RE = Ho, Er, and Tm) compounds. Particularly, the maximum value of magnetic entropy change (–ΔSM) is 21.62 J/(kg·K) under the magnetic field change (Δμ0H) of 0–5 T for Er2FeC4. The Er2FeC4 compound presenting excellent magnetocaloric performance makes it a competitive cryogenic magnetic refrigeration material.