A High Power ESR Spectrometer for Microwave Stimulated Neutron Scattering

The physical properties of magnetic condensed matter systems are typically measured while the sample is in thermal equilibrium with its surroundings. We describe the commissioning of a high power, high frequency microwave spectrometer designed to drive magnetic phases out of equilibrium while measuring the inelastic neutron scattering spectrum. A 105 (210) GHz signal is generated at 1 (0.3) W, and directed through a compact, 3D quasi-optical bridge to the sample. By tuning to a resonance condition with a magnetic field, we are able to select our excitation of interest. Reflected microwaves are detected by a heterodyne mixer, and a Martin Puplett Interferometer on the bridge isolates the reflected signal into co-polarized and cross-polarized channels. This unique design allows for compatibility with many top loading magnet systems, the power to induce a statistically significant population inversion required for neutron scattering, and the ability to do Pulsed Electron Spin Resonance experiments as a standalone unit. Performance of the system is shown by Saturation Recovery on a single crystal of Ruby with 0.05% Cr/Al by weight.