Magnetization reduction induced by nonlinear effects

TL;DR

This paper investigates how high-power microwave excitation causes a significant reduction in the magnetization component parallel to the effective field in ferromagnets, linked to nonlinear spinwave effects and relaxation rate changes.

Contribution

It provides the first detailed measurement of the longitudinal magnetization component under high-power microwave excitation and links the observed reduction to nonlinear spinwave phenomena.

Findings

$M_z$ drops dramatically at resonance saturation

Reduction in spin-lattice relaxation rate observed

Behavior linked to longitudinal spinwaves above Suhl's instability

Abstract

This letter reports the first detailed measurement of $M_z$, the component parallel to the effective field direction, when ferromagnets are excited by microwave fields at high power levels. It is found that $M_z$ drops dramatically at the saturation of the main resonance. Simultaneous measurements of $M_z$ and absorption power show that this drop corresponds to a diminution of the spin-lattice relaxation rate. These changes are interpreted as reflecting the properties of longitudinal spinwaves excited above Suhl's instability. Similar behavior should be expected in spinwave emission by currents.