FMR Damping in Thin Films with Exchange Bias

Nikolay G Chechenin,Georgy V Babaytsev,Irina O Dzhun,Irina L Romashkina,Alexey V Makunin,Mikhail G Kozin

doi:10.3390/magnetochemistry7050070

Nikolay G Chechenin, Georgy V Babaytsev + Show 4 more

Open Access

https://doi.org/10.3390/magnetochemistry7050070

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Abstract

Ferromagnetic resonance (FMR) linewidth (LW) is a tool for studying the high frequency properties of magnetic materials for their application in high-speed devices. Here, we investigate different mechanisms which determine FMR damping in bilayer ferromagnetic/antiferromagnetic (F/AF and AF/F) exchange bias systems. Variations of FMR LW with the thickness and deposition order of the F and AF layers were studied, as well as their correlation with the exchange bias field and roughness of the sample surface. We observed much larger LW in AF/F structures compared with F/AF samples. It was found that neither the exchange bias nor surface/interface roughness in the samples could explain the difference in LW for F/AF and AF/F samples. Instead, the different underlayer microstructure influenced the grainsize, leading to different angular dispersion of magnetization and different internal stray field in F-layers, promoting a different intensity of magnon scattering and FMR damping in F/AF and AF/F samples.

Highlights

The high frequency properties of ferromagnetic materials and multilayer structures are of primary importance for applications in magnetic storage devices with nanoseconds and smaller overwriting information bits
These characteristics were obtained from the fitting of the angular dependences (AD) of the resonant magnetic field, Hr(φH )
We have demonstrated that the ferromagnetic resonance (FMR) linewidth of BS samples is much larger than in TS

Summary

Introduction

The high frequency properties of ferromagnetic materials and multilayer structures are of primary importance for applications in magnetic storage devices with nanoseconds and smaller overwriting information bits. The ferromagnetic resonance (FMR) is a wellrecognized instrument for investigating the dynamics and damping of magnetization by measuring FMR linewidth (LW). Magnetization dynamics are described by the Landau–. DM/dt = −γ(M × Heff ) + (αef /Ms)(M × dM/dt), (1). The first term in the right side of (1) describes a uniform precession of the magnetic moment M in an effective magnetic field H eff. The second term is a dissipative term in the Gilbert form [2], with an effective phenomenological damping parameter αef. It describes the energy dissipation with a helical trajectory of the precessing magnetic moment. The effective magnetic field is a combination of several contributions

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