Ferromagnetic Resonance of Co/Gd and Co/Tb Multilayers

TL;DR

This study investigates the temperature-dependent ferromagnetic resonance behavior of Co/Gd and Co/Tb multilayers and trilayers, revealing exchange coupling effects and resonance shifts with temperature changes.

Contribution

It provides new experimental data and theoretical analysis on the temperature-dependent magnetic resonance properties of Co-based multilayers and trilayers.

Findings

Resonant peaks vanish around 50 K below room temperature in Co/Gd multilayers.

Exchange coupling causes a 600 Oe shift in resonance field at room temperature.

Resonance linewidth increases as temperature decreases.

Abstract

The in-plane dynamics of ferrimagnetic Co/Gd multilayers are investigated by means of ferromagnetic resonance, magneto-optical Kerr effect and SQUID magnetometry. The power absorbed from these multilayers is strongly temperature dependent. For example, the resonant peak for a (Co 40 A /Gd 40 A)8 multilayer vanishes approximately 50 K below room temperature. We have further investigated Gd/Co/Gd and Tb/Co/Tb trilayers with different thicknesses of Gd (5-7 A), Tb (1-7 A) and Co (30-40 A). At room temperature, these Co-based trilayers show a shift of approximately 600 Oe at 24 GHz in the uniform ferromagnetic resonance field, compared to pure Co film, indicating the exchange coupling between the Co and Gd. The shift in the field for the resonance increases as the temperature is decreased. Furthermore the resonance linewidth increases as the temperature is decreased. The experimental results are in good agreement with our theoretical calculations.