Ferromagnetic resonance detection by a point-contact bolometer

Abstract

We exploit nanoscale metallic contacts for detection of ferromagnetic resonance. In our experiments we use mechanical point contacts between a copper wire tip and a ferromagnetic sample of interest to inject both dc and microwave currents into the sample. A small dc voltage develops across the contact subject to microwaves that can be attributed to rectification processes in the contact. The rectification signal was found to increase linearly with the applied dc current as expected for a point contact in the thermal regime. Here the point contact acts as a nanoscale bolometer which monitors the microwave current absorbed by the sample. When the microwave absorption increases at ferromagnetic resonance the rectification signal reveals the resonance. Our point-contact technique enables the electrical detection of ferromagnetic resonance in sample volumes as small as a few cubic nanometers.