Fundamental structure of a Ni2MnGa intermediate phase having an orthorhombic lattice

摘要

Ni2MnGa is one of the attractive ferromagnetic shape memory alloys. It is reported that the parent phase is of Heusler type and transforms into an intermediate phase above M,. As regards the crystal structure of the intermediate phase, it was previously reported that the fcc main reflection remained and additional peaks appeared on cooling. This means that the long range ordered structure was produced with a cubic fundamental lattice. However, we successfully measured peak splitting of the fundamental reflections from the intermediate phase using high energy synchrotron radiation. Careful analyses with the whole pattern decomposition method were carried out and clear evidence of an orthorhombic fundamental lattice with lattice constants a = 5.8285, b = 5.8142 and c = 5.7886 angstrom is presented.