Theoretical study of complex susceptibility of Pd and Pt

Spin transfer torque in a multilayer magnetic system can be understood in terms of interaction between a normal metal and a ferromagnetic layer on the multilayer, in which the interaction is characterized by the magnetic susceptibility. Most of experimental studies on this subject utilizes heavy metals, such as Pd and Pt, while a recent theory assumes a light metal as the normal metal. We aim to reconcile this discrepancy and achieve consistency with the experiments by studying magnetic susceptibility of Pd and Pt. We theoretically investigate the complex magnetic susceptibility of Pd and Pt by combining Tight-binding Approximation, Hubbard Model, and Density Functional Theory. We calculate a single band susceptibility for Pd and Pt. Our results show that the band structure is dominated by the d-orbitals and the susceptibility is enhanced by its large repulsive interaction.