Electron-Phonon Coupling Parameter of Ferromagnetic Metal Fe and Co.

Kyuhwe Kang,Gyung-Min Choi

doi:10.3390/ma14112755

Kyuhwe Kang, Gyung-Min Choi

Open Access

https://doi.org/10.3390/ma14112755

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Journal: Materials	Publication Date: May 23, 2021
Citations: 6	License type: CC BY 4.0

Affiliation: Sungkyunkwan University, Institute for Basic Science

Abstract

The electron-phonon coupling (g) parameter plays a critical role in the ultrafast transport of heat, charge, and spin in metallic materials. However, the exact determination of the g parameter is challenging because of the complicated process during the non-equilibrium state. In this study, we investigate the g parameters of ferromagnetic 3d transition metal (FM) layers, Fe and Co, using time-domain thermoreflectance. We measure a transient increase in temperature of Au in an FM/Au bilayer; the Au layer efficiently detects the strong heat flow during the non-equilibrium between electrons and phonons in FM. The g parameter of the FM is determined by analyzing the temperature dynamics using thermal circuit modeling. The determined g values are 8.8–9.4 × 1017 W m−3 K−1 for Fe and 9.6–12.2 × 1017 W m−3 K−1 for Co. Our results demonstrate that all 3d transition FMs have a similar g value, in the order of 1018 W m−3 K−1.

Highlights

Introduction of Ferromagnetic Metal Fe andCo.The ultrafast photoexcitation, triggered by femtosecond laser pulse, of metallic surfaces has enabled the investigation of the thermal relaxation process between excited electrons and phonons in metals
This parameter has been studied for ferromagnetic 3d transition metals (FMs) to understand the ultrafast dynamics of magnetization
We demonstrated that the g parameter can be accurately determined by measuring the transient heat current from Ni to Au in a Ni/Au bilayer, and determined the g parameter of Ni to be 8.6 × 1017 W m−3 K−1 [11]

Summary

Introduction

Introduction of Ferromagnetic Metal Fe andCo.The ultrafast photoexcitation, triggered by femtosecond laser pulse, of metallic surfaces has enabled the investigation of the thermal relaxation process between excited electrons and phonons in metals. A key parameter for the ultrafast thermal relaxation in metals is the electron–phonon coupling (g), which has been reported for several materials [2,3,4,5,6,7,8]. This parameter has been studied for ferromagnetic 3d transition metals (FMs) to understand the ultrafast dynamics of magnetization. The exact determination of the g parameter from the temperature responses of the FM is often challenging because of multiple couplings among electrons, phonons, and magnons

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Results

Conclusion