Theoretical treatment and direct measurements of magnetocaloriceffect in Ni2.19−xFexMn0.81Ga Heusler alloys

Magnetocaloric effect in a series of Ni2.19−xFexMn0.81Ga (x=0.01-0.04) Heusler alloys has been studied experimentally by direct measurements of the adiabatic temperature change ΔTad and theoretically by means of classical Monte Carlo simulations. The direct measurements of ΔTad have shown that the adiabatic temperature change measured in the vicinity of the first-order magnetostructural phase transition and at the Curie temperature of austenite TC is practically the same, ΔTad≈1.6 K, for the magnetic field change ΔHext=2 T. On the basis of theoretical methods, the magnetic exchange interaction constants, the temperature dependencies of the magnetization and the adiabatic temperature change have been calculated. Results of the simulations are in a fair agreement with the experimental data.