Static and Microwave Properties of Amorphous Magnets Near Saturation

TL;DR

This paper investigates the static and dynamic behaviors of amorphous ferromagnets near saturation, revealing how randomness influences spin correlations, damping, and localization of excitations through analytical, numerical, and simulation methods.

Contribution

It provides a detailed analysis of how weak external fields and anisotropy affect magnetization near saturation, highlighting the role of randomness in spin localization and damping.

Findings

Spin-spin correlations scale with parameters as confirmed by simulations.

Near ferromagnetic resonance, spin excitations are damped and localized due to randomness.

Increasing randomness reduces localization length and increases damping of spin excitations.

Abstract

Static and dynamic properties of magnetically soft amorphous ferromagnets have been studied analytically and numerically within random-field and random-anisotropy models. External field and coherent anisotropy that are weak compared to their random counterparts are sufficient to bring the magnet close to saturation. The scaling of spin-spin correlations in this regime is computed, and its dependence on parameters is confirmed by Monte Carlo simulation. We show that near the ferromagnetic resonance, the spin excitations are damped and spatially localized due to randomness even close to saturation. On increasing the strength of randomness, the localization length goes down in accordance with theoretical expectations, while the damping of spin excitations goes up.