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 Ni2MnSn and Ni1.92Mn1.56Sn0.52 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 TM-A was observed in the Ni1.92Mn1.56Sn0.52 compound. The coefficient dT(M-A)/dp reached value of 18 K/GPa. The already low value of martensite magnetization of Ni1.92Mn1.56Sn0.52 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 TM-A of Ni1.92Mn1.56Sn0.52 at zero field. An anomalous increase of resistivity of the compound has been observed at temperature range below TM-A, however, it does not copy the sharp change of magnetization at TM-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. (C) 2015 Elsevier B.V. All rights reserved.