Current induced magnetization dynamics in current perpendicular to the plane spin valves

TL;DR

This paper investigates how spin transfer torque induces magnetization dynamics in current-perpendicular-to-plane spin valves, revealing how noise spectra evolve with magnetic configuration and current, and demonstrating significant resistance noise effects.

Contribution

It provides detailed experimental insights into the current-induced magnetization dynamics and noise behavior in CPP-GMR spin valves, highlighting the dependence on magnetic configuration and current direction.

Findings

Noise spectra evolve from a peak to 1/f noise with magnetic configuration changes.

Resistance noise amplitude increases with current and saturates at a significant fraction of magnetoresistance.

Magnetization dynamics are only observed when spin transfer reorients the free layer away from the magnetic field direction.

Abstract

We observe magnetization dynamics induced by spin momentum transfer in the noise spectra of current perpendicular to the plane giant magnetoresistance spin valves. The dynamics are observable only for those combinations of current direction and magnetic configuration in which spin transfer acts to reorient the free layer magnetization away from the direction set by the net magnetic field. Detailed measurements as a function of magnetic configuration reveal an evolution of the noise spectra, going from a spectrum with a well-defined noise peak when the free layer is roughly collinear with the pinned layer to a spectrum dominated by 1/f noise when the free layer is in an orthogonal configuration. Finally, the amplitude of the corresponding resistance noise increases rapidly with increasing current until it saturates at a value that is a substantial fraction of the magnetoresistance between parallel and antiparallel states.