About the significance of the driving current direction in ferromagnetic resonance experiments

TL;DR

This study investigates how the direction of driving current affects ferromagnetic resonance in NiFe foils, revealing shape-dependent behaviors and the importance of current distribution in experimental outcomes.

Contribution

It demonstrates the influence of current direction on resonance fields and introduces a method to control contributions from different current paths in ferromagnetic resonance experiments.

Findings

Resonance field follows a cos dependence on current angle in rectangular samples.

Triangular samples show three independent cos features from different current paths.

Covering an edge can switch off specific current contributions, affecting resonance behavior.

Abstract

We present an experimental study of the effects of driving current direction on ferromagnetic resonance in NiFe foils. The rf driving current was applied to NiFe foils of different shapes. In rectangular samples with a close-to-uniform flow of the applied current along the long edge of the sample we find the resonance field to follow a simple 'cos' dependence on the angle between the current and external dc magnetic field. We argue that this behavior cannot be explained by the in-plane demagnetizing field of the rectangular foil. In triangular samples where the current partially flows along all three sample edges we observed three independent 'cos' features. The latter suggests individual contributions from different areas with different current directions. We were able to switch off one of these contributions by covering one edge of the triangular sample with a conducting overlayer and thereby effectively short-circuiting the corresponding current path. Our findings highlight the significance of driving current distributions in ferromagnetic resonance experiments.