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

Intrinsic magnetic properties and magnetocaloric effect (MCE) have been investigated for Hf 1− x Ta x Fe 2 ( 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 ΔS M and the adiabatic temperature change Δ T ad are enhanced. An adiabatic temperature change of Δ T ad = 2 and 2.5 K was observed in Hf 0.875 Ta 0.125 Fe 2 and Hf 0.825 Ta 0.175 Fe 2 , 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 Hf 1− x Ta x Fe 2 systems. In addition substitution can be used to tune both the transition temperature but also the magnetic transition from first toward second order type. [ABSTRACT FROM AUTHOR]