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 (T_C) 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 T_C = 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 (–ΔS_M) 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.