Magnetic-field-induced phase transitions in Heusler Ni$_{2.16}$Mn$_{0.84}$Ga alloy and single crystal MnAs in fields up to 14 T

The paper presents the results of a comparison of the isothermal heat release values in the Heusler Ni$_{2.16}$Mn$_{0.84}$Ga alloy and the MnAs single crystal, determined by direct and indirect methods in the region of magnetic and magnetostructural phase transitions in high magnetic fields up to 14 T. It was found that at a magnetic field strength sufficient to complete the magnetic-field-induced phase transition, the results obtained using direct and indirect methods coincide with good accuracy. The maximum value of isothermal heat $q$ $=$ 5.25 kJ/kg was obtained by the direct method for the Heusler Ni$_{2.16}$Mn$_{0.84}$Ga alloy at $\mu_0H$ $=$ 14 T during cooling, and $q$ $=$ 9.3 kJ/kg was obtained for the MnAs single crystal at $\mu_0H$ $=$ 10 T during heating.