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Giant magnetocaloric effect in the quaternary Fe–Rh–Pd–Ir alloy: Experimental and first-principles study
The magnetothermal properties of the quaternary Fe49Rh46.1Pd3.1Ir1.8 alloy are investigated by a combination of first-principles calculations, structural characterization, magnetometry, calorimetry, and direct measurements of the adiabatic temperature change. An exceptional magnetocaloric response is obtained, with ΔTad reaching −11.9 K in a field of 1.85 T under the discontinuous protocol and −8.6 K under the continuous (cyclic) protocol, both values exceeding those reported to date for FeRh-based alloys under comparable conditions. The enhancement originates from a combination of structural and electronic properties: a nearly single-phase B2 composition, induced magnetic moments on Pd and Ir predicted by first-principles calculations, and a narrow magnetostructural transition (∼6 K). In addition, the present composition exhibits an exceptionally small thermal hysteresis of ∼6 K, which is among the smallest reported for the FeRh family and preserves a large magnetocaloric response under cyclic operation. The high transition temperature of ∼411 K further distinguishes the present composition from conventional near-room-temperature magnetocaloric systems. The temperature dependences of the lattice parameter, magnetization, heat capacity, and magnetocaloric response are presented and compared with literature data for binary and ternary FeRh-based alloys.