Microstrip resonators for electron paramagnetic resonance experiments

Abstract

In this article we evaluate the performance of an electron paramagnetic resonance (EPR) setup using a microstrip resonator (MR). The design and characterization of the resonator are described and parameters of importance to EPR and spin manipulation are examined, including cavity quality factor, filling factor, and microwave magnetic field in the sample region. Simulated microwave electric and magnetic field distributions in the resonator are also presented and compared with qualitative measurements of the field distribution obtained by a perturbation technique. Based on EPR experiments carried out with a standard marker at room temperature and a MR resonating at 8.17 GHz, the minimum detectable number of spins was found to be 5 x 10(10) spins/GHz(1/2) despite the low MR unloaded quality factor Q0=60. The functionality of the EPR setup was further evaluated at low temperature, where the spin resonance of Cr dopants present in a GaAs wafer was detected at 2.3 K. The design and characterization of a more versatile MR targeting an improved EPR sensitivity and featuring an integrated biasing circuit for the study of samples that require an electrical contact are also discussed.

Quantitative Modeling of Superconducting Planar Resonators for Electron Spin Resonance

“…While conventional ESR resonators based on three-dimensional (3D) microwave cavities provide a microwave magnetic field with high homogeneity over a large volume, they suffer from small filling factors and, in turn, a low sensitivity for small samples. Planar microresonators allow to reduce the mode volume, which, depending on the sample size and geometry, can lead to an increased filling factor and therefore an enhanced sensitivity compared to 3D cavities [3][4][5] . In addition, planar resonators operated at low temperatures allow one to use superconducting materials, offering small losses and extraordinarily high quality factors.…”

Metallic coplanar resonators optimized for low-temperature measurements

“…The observation can be explained by the magnetoresistance of copper at higher fields [35]. Planar structures (microstrip, stripline and coplanar) have already been employed for ESR experiments [15,[36][37][38][39][40][41][42][43][44][45][46]. Although microstrip and stripline resonators have also been successfully applied in ESR measurements [36-38, 41, 45, 47], coplanar configurations might be more appropriate candidates since they carry the signal non-dispersively in contrast to a microstrip configuration [45,48].…”

Modeling of Dielectric Resonator Antennas using Numerical Methods Applied to EPR

“…In general there are some specific types of EPR resonators, say wave-guide resonator, microstrip resonator, dielectric resonator, and transmission line resonator [83]. Unlike traditional EPR waveguide cavities operating in the transverse electric TE mode, on which both longitudinal and transverse dimensions scale with frequency, transmission-line resonators operating in the transverse electromagnetic (TEM) mode have their resonant frequency set only by the longitudinal dimension and the effective relative permittivity of the medium (εref) which ultimately results in shorter transverse dimensions than half wavelength [84]. As per [85] the conventional EPR systems i.e.…”