Magneto-structural transitions induced at 1.2 K in Ni2MnGa-based Heusler alloys by high magnetic field up to 60 T

Abstract

The huge decrease of the martensitic transition temperature TM–A with increasing field (up to dTM–A /dH = −8.1 K T−1) was observed in all the Co-doped and In-doped Ni50 − xCoxMn25 + yGa25 − y − zInz Heusler alloys at high pulse magnetic field up to 60 T. The structural martensitic transitions were induced at temperatures 2 K and 1.2 K in the Ni1.72Co0.28Mn1.25Ga0.75 and Ni1.65Co0.34Mn1.31Ga0.62In0.07 alloys, respectively. The transitions are accompanied by a significant increase of magnetization of their austenite phase with increasing field up to MA(2 K) = 6.3 μB/f.u. The very slight increase of magnetization of their martensite phase MM(2 K) was induced by the high magnetic field in both, the stoichiometric Ni2MnGa and the off-stoichiometric Ni1.65Co0.34Mn1.31Ga0.62In0.07 alloys. The presented results demonstrate the key role of magnetism in the martensitic transitions in the Ni2MnGa based Heusler alloys and point to the Jahn–Teller effect as a source of the tetragonal distortion of crystal structure of these alloys.