Pre-martensitic phenomena in a near stoichiometric Ni _2 MnGa Polycrystalline alloy

Abstract

The internal friction, the elastic modulus and the AC magnetic susceptibility of a near stoichiometric Ni2MnGa polycrystalline sample with low transition temperatures have been measured as a function of temperature by resonant ultrasound spectroscopy (RUS) and superconducting quantum interference device (SQUID) measurements. An internal friction peak and two minima in the elastic modulus have been observed, corresponding to the weakly first order transition from the cubic L2 _{1} parent phase to the intermediate phase (at T_{I} ≅ 213 K) and to the Martensitic Transformation (at T_{M} ≅ 100 K). The real part of the magnetic susceptibility shows a decrease and the imaginary part a peak at T_{I} .