Magnetic and magnetocaloric properties of itinerant-electron system Hf1−xTaxFe2 (x = 0.125 and 0.175)

• First report of the direct measurement of ΔTad in Hf1−xTaxFe2 compounds.
• ΔTad reach values of 2.5 K under μ0ΔH = 3 T for x = 0.175 compound.
• A field induced metamagnetic phase transition has been observed.

Intrinsic magnetic properties and magnetocaloric effect (MCE) have been investigated for Hf1−xTaxFe2 (x = 0.125 and 0.175) itinerant-electron compounds which exhibit a temperature-induced transition from the ferromagnetic (FM) to the antiferromagnetic (AFM) state. Upon increasing Ta concentration, the ferromagnetic ordering temperature strongly decreases with decreasing the lattice parameters and both the isothermal magnetic entropy change ΔSM and the adiabatic temperature change ΔTad are enhanced. An adiabatic temperature change of ΔTad = 2 and 2.5 K was observed in Hf0.875Ta0.125Fe2 and Hf0.825Ta0.175Fe2, respectively, for a magnetic field change of 3 T. Therefore, the partial substitution of Ta for Hf is highly effective in the enhancement of the magnetocaloric effect in Hf1−xTaxFe2 systems. In addition substitution can be used to tune both the transition temperature but also the magnetic transition from first toward second order type.