Field-Induced Martensitic Transformation in New Ferromagnetic Shape Memory Compound Mn_1.07Co_0.92Ge

Abstract

The structural transformation of a ferromagnetic Mn1.07Co0.92Ge compound was studied by magnetization measurement in magnetic fields up to 13 T and powder X-ray diffraction measurement in fields up to 5 T. The Curie temperature is determined to be 275 K. At room temperature, the compound has a hexagonal Ni2In-type structure, and it transforms diffusionlessly into an orthorhombic TiNiSi-type structure at MS=210 K with hysteresis. The cell volume expands by 5.3% and the magnetic moment increases by 24% at MS, accompanied with this martensitic structural transformation. In addition, we confirmed for the first time that magnetic field induces the structural transformation in Mn1.07Co0.92Ge at the vicinity of MS.