Multipurpose High Frequency Electron Spin Resonance Spectrometer for Condensed Matter Research

TL;DR

This paper presents a versatile, high-frequency ESR spectrometer operating between 75-225 GHz, optimized for condensed matter research, with sensitivity comparable to commercial spectrometers and adaptable probe heads for diverse applications.

Contribution

The development of a robust, easy-to-use multifrequency ESR spectrometer with high sensitivity and versatile probe options for condensed matter, chemistry, and biology research.

Findings

Achieved sensitivity of 2x10^10 spins/G/Hz^{1/2} at 222.4 GHz

Demonstrated spectrometer's capability with examples from condensed matter physics

Operable by undergraduate students

Abstract

We describe a quasi-optical multifrequency ESR spectrometer operating in the 75-225 GHz range and optimized at 210 GHz for general use in condensed matter physics, chemistry and biology. The quasi-optical bridge detects the change of mm wave polarization at the ESR. A controllable reference arm maintains a mm wave bias at the detector. The attained sensitivity of 2x10^10 spin/G/(Hz)1/2, measured on a dilute Mn:MgO sample in a non-resonant probe head at 222.4 GHz and 300 K, is comparable to commercial high sensitive X band spectrometers. The spectrometer has a Fabry-Perot resonator based probe head to measure aqueous solutions, and a probe head to measure magnetic field angular dependence of single crystals. The spectrometer is robust and easy to use and may be operated by undergraduate students. Its performance is demonstrated by examples from various fields of condensed matter physics.