Direct measurements of the magnetocaloric effect in samples of rapidly quenched ribbons of ${\text{Mn}}_{50}{\text{Ni}}_{40}{\text{In}}_{10}$ and ${\text{Ni}}_{50}{\text{Mn}}_{37}{\text{Sn}}_{13}$ Heusler alloys with potential applications in magnetic refrigeration technology are carried out. The measurements were made by a precise method based on the measurement of the oscillation amplitude of the temperature in the sample while is subjected to a modulated magnetic field. In the studied compositions both direct and inverse magnetocaloric effects associated with magnetic (paramagnet-ferromagnet-antiferromagnet) and structural (austenite-martensite) phase transitions are found. Additional inverse magnetocaloric effects of small value are observed around the ferromagnetic transitions.

Monte Carlo simulations were used for a detailed description of magnetic, martensitic and magnetocaloric properties of Ni_2+x Mn_1−x Ga (0.18 ⩽ x ⩽ 0.24) and Ni₅₀Mn₃₄In₁₆ Heusler alloys, which undergo a first-order magnetostructural phase transition. In the simulations we made use of magnetic exchange parameters which were obtained by ab initio calculations. Results of magnetic and lattice contributions to the total specific heat as well as the change in the isothermal magnetic entropy ΔS _mag and the adiabatic temperature ΔT _ad changes around the magnetic and magnetostructural transitions in an external magnetic field agree fairly well with available experimental data.