An interpretation of martensitic transformation in L1₂-type Fe₃Pt from its electronic structure

Partly ordered Fe₃Pt is one of ferromagnetic shape memory alloys exhibiting a large magnetic field-induced strain in its martensite phase formed by a second-order-like martensitic transformation from the L1₂-type structure to the so-called FCT martensite (L6₀-type structure). We have investigated the origin of this transformation from their electronic structures calculated in the present study. A characteristic feature in the electronic structure is the existence of a relatively high peak in the density of states of the minority spin band just below the Fermi energy. This peak splits into two peaks by tetragonal distortion, and one of them shifts to lower energy by the distortion, suggesting that the band Jahn-Teller effect is the main cause for the transformation.