Origin of large magnetostriction in palladium cobalt and palladium nickel alloys: Strong pseudo-dipole interactions between palladium–cobalt and palladium–nickel atomic pairs

Abstract

The origin of the large magnetostriction in palladium cobalt and palladium nickel alloys was investigated. Density functional theory calculations based on the Korringa–Kohn–Rostoker Green function method with the coherent potential approximation revealed that alloying with palladium results in increased magnetization of cobalt and nickel atoms. Also, anomalous magnetization of palladium atoms occurs simultaneously. Employing calculated spin and orbital angular momenta of the atoms, magnetostriction was discussed based on the two-spin model for disordered alloys. Under the assumption that the pseudo-dipole interaction is proportional to the orbital and total angular momenta, the experimental magnetostriction curves can be reproduced. The estimated contributions of each atomic pair to magnetostriction revealed that the large magnetostriction at the palladium-rich side originates from the strong pseudo-dipole interactions between 4d and 3d transition metal atoms, namely, palladium–cobalt and palladium–nickel atomic pairs.