Observing electron spin resonance between 0.1 and 67 GHz at temperatures between 50 mK and 300 K using broadband metallic coplanar waveguides

TL;DR

This paper presents a broadband ESR technique using metallic coplanar waveguides, enabling continuous tuning over wide frequency and temperature ranges, applicable to various sample types and surpassing conventional ESR capabilities.

Contribution

It introduces a fully broadband ESR method with metallic coplanar waveguides, allowing continuous frequency and magnetic field tuning from 50 mK to 300 K and 0.1 to 67 GHz.

Findings

Successful ESR measurements across wide frequency and temperature ranges.

Versatile application to different sample types.

Enhanced parameter space compared to traditional ESR methods.

Abstract

We describe a fully broadband approach for electron spin resonance (ESR) experiments where it is possible to not only tune the magnetic field but also the frequency continuously over wide ranges. Here a metallic coplanar transmission line acts as compact and versatile microwave probe that can easily be implemented in different cryogenic setups. We perform ESR measurements at frequencies between 0.1 and 67 GHz and at temperatures between 50 mK and room temperature. Three different types of samples (Cr3+ ions in ruby, organic radicals of the nitronyl-nitroxide family, and the doped semiconductor Si:P) represent different possible fields of application for the technique. We demonstrate that an extremely large phase space in temperature, magnetic field, and frequency for ESR measurements, substantially exceeding the range of conventional ESR setups, is accessible with metallic coplanar lines.