Electronic and magnetic trends in martensitically transforming Fe–Pd alloys

We discuss the compositional trends in the electronic structure of Fe–Pd alloys in the composition range relevant for martensitic transformations and magnetic shape-memory applications. The results are obtained within the framework of density functional theory based on the Korringa–Kohn–Rostoker Green's function approach in combination with the coherent potential approximation for the description of disorder. For the body centered cubic structure, we observe with increasing Pd content the gradual disappearance of the pseudogap like structure in the center of the minority spin d-band, while on the face centered cubic side a small peak passes the Fermi level around 80 at. % Fe, which has been related previously to a band-Jahn–Teller instability. In addition, we investigate the structural variation of magnetic properties of the magnetic shape-memory composition Fe70Pd30 based on magnetic exchange parameters obtained from our ab initio calculations being mapped onto a classical Heisenberg model. This allows us to estimate the magnetic transition temperature within a mean field approach and Monte Carlo simulations taking into account the induced nature of the Pd atoms, leading to a close, semi-quantitative agreement with experiment in the latter case.

► Compositional trends in the electronic structure from density functional theory.
► Bcc minority-spin pseudogap disappears with increasing Pd content.
► Band-Jahn-Teller peak passes the Fermi level in the fcc minority-spin channel.
► Modified Heisenberg model with ab initio parametrization for magnetic properties.
► Structural trends in the Curie temperatures are almost quantitatively reproduced.