Spectroscopy of phonons and spin torques in magnetic point contacts

TL;DR

This study uses phonon spectroscopy to explore how impurity scattering influences current-induced spin torques in magnetic point contacts, revealing that scattering at the interface is crucial for the observed effects.

Contribution

It demonstrates that impurity scattering at the N/F interface is the key mechanism behind the spin torque effect in magnetic point contacts.

Findings

Magnetization excitations are prominent in diffusive and thermal contacts.

No magnetic excitations are observed in highly ballistic contacts.

Impurity scattering at the interface causes the spin torque effect.

Abstract

Phonon spectroscopy is used to investigate the mechanism of current-induced spin torques in nonmagnetic/ferromagnetic (N/F) point contacts. Magnetization excitations observed in the magneto-conductance of the point contacts are pronounced for diffusive and thermal contacts, where the electrons experience significant scattering in the contact region. We find no magnetic excitations in highly ballistic contacts. Our results show that impurity scattering at the N/F interface is the origin of the new single-interface spin torque effect.