Effect of pressure and high magnetic field on phase transitions and magnetic properties of Ni_1.92Mn_1.56Sn_0.52 and Ni₂MnSn Heusler compounds

Complex study of magnetic, magnetocaloric and structural properties of the Ni₂MnSn and Ni_1.92Mn_1.56Sn_0.52 compounds was performed. The stoichiometric single-crystal of Ni₂MnSn was prepared by Czochralski method. The remarkable pressure effect on the martensitic magnetization and the martensite-austenite transition temperature T_M–A was observed in the Ni_1.92Mn_1.56Sn_0.52 compound. The coefficient dT_M–A/dp reached value of 18 K/GPa. The already low value of martensite magnetization of Ni_1.92Mn_1.56Sn_0.52 was further substantially decreased by external pressure, in contrast with pressure almost insensitive magnetization of the stoichiometric Ni₂MnSn single-crystal. The pulse magnetic field of 58 T invoked the structural transition at temperature 180 K that is of about 100 K below T_M–A of Ni_1.92Mn_1.56Sn_0.52 at zero field. An anomalous increase of resistivity of the compound has been observed at temperature range below T_M–A, however, it does not copy the sharp change of magnetization at T_M–A. The obtained results indicate the important role of interatomic distances on the magnetic ordering and electronic structure of the studied Heusler alloys and are in agreement with the Jahn-Teller mechanism of the martensitic transition in these compounds.