The influence of atomic order on the magnetic and structural properties of the ferromagnetic shape memory compound Ni2MnGa

The effect of atomic order on the martensitic phase transition and magnetic properties of stoichiometric Ni2MnGa has been investigated in a sample quenched from 1000 ◦C. Magnetization, resistivity and x-ray diffraction measurements indicate that the structural phase transition occurs at ~103 K, substantially lower than the value reported for samples quenched from 800 ◦C and ordered in theHeusler L21 structure. Asmall reduction in the ferromagnetic moment was also observed, although the Curie temperature remained largely unaffected. The electronic Sommerfeld coefficient obtained from heat capacity measurements is enhanced but smaller than that observed for the 800 ◦C quenched sample. The results are consistent with band structure calculations and the electronic changes brought about by atomic disorder.