Electron-Phonon Scattering governs both Ultrafast and Precessional Magnetization Dynamics in Co-Fe Alloys

TL;DR

This study investigates how electron-phonon interactions influence ultrafast and precessional magnetization dynamics in Co-Fe alloys, revealing compositional dependencies that impact energy-efficient magnetic storage technologies.

Contribution

It provides the first comprehensive analysis linking electron-phonon interactions to femto- to nano-second magnetization dynamics in Co-Fe alloys using TRMOKE and theoretical models.

Findings

Low Gilbert damping correlates with prolonged ultrafast demagnetization.

Magnetization dynamics strongly depend on electron-phonon interaction strength.

Compositional tuning can optimize magnetic response for spintronics.

Abstract

Recent investigations have advanced the understanding of how structure-property relationships in ferromagnetic metal alloys affect the magnetization dynamics on nanosecond time-scales. A similar understanding for magnetization dynamics on femto- to pico-second time-scales does not yet exist. To address this, we perform time-resolved magneto optic Kerr effect (TRMOKE) measurements of magnetization dynamics in Co-Fe alloys on femto- to nano-second regimes. We show that Co-Fe compositions that exhibit low Gilbert damping parameters also feature prolonged ultrafast demagnetization upon photoexcitation. We analyze our experimental TR-MOKE data with the three-temperature-model (3TM) and the Landau-Lifshitz-Gilbert equation. These analyses reveal a strong compositional dependence of the dynamics across all time-scales on the strength of electron-phonon interactions. Our findings are beneficial to the spintronics and magnonics community, and will aid in the quest for energy-efficient magnetic storage applications.