Towards tailoring the magnetocaloric response in FeRh-based ternary compounds

In this work, we demonstrate that the magnetocaloric response of FeRh-based compounds may be tailored for potential magnetic refrigeration applications by chemical modification of the FeRh lattice. Alloys of composition Fe(Rh1−xAx) or (Fe1−xBx)Rh (A = Cu, Pd; B = Ni; 0 < x < 0.06) were synthesized via arc-melting and subsequent annealing in vacuum at 1000 °C for 48 h. The magnetocaloric properties of the FeRh-based systems were determined using isothermal M(H) curves measured in the vicinity of the magnetostructural temperature (Tt). It is found that the FeRh working temperature range (δTFWHM) may be chemically tuned over a wide temperature range, 100 K ≤ T ≤ 400 K. While elemental substitution consistently decreases the magnetic entropy change (ΔSmag) of the FeRh-based ternary alloys from that of the parent FeRh compound (ΔSmag,FeRh ∼ 17 J/kg K; ΔSmag,FeRh-ternary = 7–14 J/kg K at Happ = 2 T), the net refrigeration capacity (RC), defined as the amount of heat that can be transferred during one magnetic refrigeration cycle, of the modified systems is significantly higher (RCFeRh ∼ 150 J/kg; RCFeRh-ternary = 170–210 J/kg at Happ = 2 T). These results are attributed to stoichiometry-induced changes in the FeRh electronic band structure and beneficial broadening of the magnetostructural transition due to local chemical disorder.