Theoretical analysis of FMR-driven spin pumping current and its properties via Self-Consistent Harmonic Approximation

TL;DR

This paper employs the Self-Consistent Harmonic Approximation to analyze ferromagnetic resonance-driven spin pumping in ferromagnetic/normal metal junctions, revealing temperature-dependent behaviors and key magnetic properties with results aligning well with existing literature.

Contribution

It introduces the use of SCHA combined with coherent states to study FMR spin pumping, providing a novel theoretical framework for analyzing magnetic interface phenomena.

Findings

Temperature dependence of FMR-driven spin pumping characterized.

Calculated spin-mix conductance and damping parameters.

Results agree with previous experimental and theoretical studies.

Abstract

We applied the Self-Consistent Harmonic Approximation (SCHA), combined with coherent states formalism, to study the ferromagnetic resonance (FMR) in a ferromagentic/normal metal junction. Due to the interface interaction, the FMR-generated spin current is injected from the magnetic insulator to the normal metal, the so-called spin pumping. Ordinarily, ferromagnetic models are described by bosonic representation or phenomenological theories; however, in a coherent magnetization state, the SCHA is the more natural choice to treat FMR problems. Over the years, the SCHA has successfully applied to investigate ferro and antiferromagnetism in a wide range of scenarios. The main point of the SCHA formalism involves the adoption of a quadratic model for which corrections are included through temperature-dependent renormalization parameters. Therefore, the SCHA is an efficient method for determining the properties of magnetically ordered phases. Using the SCHA, we obtained the temperature dependence of FMR-driven spin pumping. In addition, we found the spin-mix conductance, the additional damping from the angular momentum injection into the normal metal side, and the magnetic susceptibility. The SCHA outcomes are in remarkable agreement with the results of the literature.