Effect of pressure and high magnetic field on phase transitions and magnetic properties of Ni1.92Mn1.56Sn0.52 and Ni2MnSn Heusler compounds.

Complex study of magnetic, magnetocaloric and structural properties of the Ni 2 MnSn and Ni 1.92 Mn 1.56 Sn 0.52 compounds was performed. The stoichiometric single-crystal of Ni 2 MnSn 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 1.92 Mn 1.56 Sn 0.52 compound. The coefficient dT M–A /dp reached value of 18 K/GPa. The already low value of martensite magnetization of Ni 1.92 Mn 1.56 Sn 0.52 was further substantially decreased by external pressure, in contrast with pressure almost insensitive magnetization of the stoichiometric Ni 2 MnSn 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 1.92 Mn 1.56 Sn 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. [ABSTRACT FROM AUTHOR]