Magnetic properties and magnetocaloric effect of Hf–Ta–Fe–(CO) alloys

The as-cast intermetallic compounds Hf0.8Ta0.2Fe1.98−xCox (x=0, 0.02 and 0.04) show a temperature or magnetic field induced first-order magnetic transition (FOMT) between aferromagnetic (F) and anantiferromagnetic (AF) state. The maximum magnetic entropy change (|ΔS|) is about 4.8 J/kg K when x=0 in a magnetic field change of 5 T. A small amount of Co substitution for Fe does not significantly reduce the maximum |ΔS| but broadens the working temperature range.