Temperature Dependent Ferromagnetic Resonance via the Landau-Lifshitz-Bloch Equation: Application to FePt

TL;DR

This paper derives temperature-dependent ferromagnetic resonance spectra using the Landau-Lifshitz-Bloch equation, providing insights into how resonance frequency and damping vary with temperature in FePt, with applications to larger structures.

Contribution

It introduces an analytic approach to model temperature effects on FMR spectra using the LLB equation, applied to FePt and extended to larger structures with GPU acceleration.

Findings

Resonance frequency decreases with temperature.

Damping increases with temperature.

Size effects influence resonance properties.

Abstract

Using the Landau-Lifshitz-Bloch (LLB) equation for ferromagnetic materials, we derive analytic expressions for temperature dependent absorption spectra as probed by ferromagnetic resonance (FMR). By analysing the resulting expressions, we can predict the variation of the resonance frequency and damping with temperature and coupling to the thermal bath. We base our calculations on the technologically relevant L1$_0$ FePt, parameterised from atomistic spin dynamics simulations, with the Hamiltonian mapped from ab-initio parameters. By constructing a multi-macrospin model based on the LLB equation and exploiting GPU acceleration we extend the study to investigate the effects on the damping and resonance frequency in ${\mu}$m sized structures.