Band Jahn Teller Like Distortion In TiPd Shape Memory Alloy On Addition Of Magnetic Impurity Co

Abstract

In this paper, we have reported the electronic structure and magnetic properties of TiPd alloyed with two different concentrations of magnetic impurity Co in the framework of density functional theory using the full potential linearized augmented plane wave method. The prominent high temperature shape memory alloy (HTSMA) - TiPd, undergoes martensitic transformation from the parent B2 (cubic) phase to the product B19 (orthorhombic) phase. Among the two configurations [Ti(Pd,Co) and (Ti,Co)Pd] considered, Co is found to prefer Ti sublattice more than the Pd sublattice from the formation energy calculations for both B2 and B19 phases. The addition of Co induced magnetic behaviour in the compounds investigated. The densities of states (total, site and angular momentum decomposed) are studied in detail. Band Jahn Teller (BJT) effects are used to understand structural instability in solids. In BJT, the peak in the vicinity of Fermi level, in the spin down channel of the high symmetry phase splits or broadens on deformation. A band Jahn Teller like broadening is observed in the density of states curve of Ti25Pd50Co25. This broadening is accompanied by a decrease in electronic energy and number of states at Fermi level. BJT effect is an accompanying feature of martensitic transformation.