ESR imaging in solid phase down to sub-micron resolution: methodology and applications

Abstract

Electron spin resonance microcopy (ESRM) is an imaging method aimed at the observation of paramagnetic species in small samples with micron-scale spatial resolution. At present, this technique is pursued mainly for biological applications at room temperature and in relatively low static magnetic fields. This work is focused on the use of ESRM for the measurement of solid samples. First, a brief comparison of various electron spin resonance (ESR) detection techniques is provided, with an emphasis on conventional "induction detection". Following that, some methodological details are provided along with experimental examples carried out at room temperature and in a static field of approximately 0.5 T. These examples show for the first time the imaging of solid samples measured by "induction detection" ESR with a resolution better than 1 mum. Based on these experimental examples and capabilities, an outlook for the future prospects of this methodology in terms of spin sensitivity and resolution is provided. It is estimated that single-spin sensitivity could be achieved for some samples at liquid-helium temperatures and static fields of approximately 2 T. Furthermore, under these conditions, spatial resolution could reach the nanometer scale. Finally, a description of possible applications of this new methodology is provided.

Dielectric Ceramic EPR Resonators for Low Temperature Spectroscopy at X-band Frequencies

“…Rutile was reported as suitable material for DRs [14] but it often contains residual impurities. Furthermore, it features substantial temperature dependencies of the stability of e r ; s e and of tan d between 6 and 300 K [15]. A discussion of the DR materials sapphire and rutile as well as perovskite-based ceramics is presented in the work of Golovina et al [11], where the authors express the need of high dielectric permittivity materials for low cost employability of DRs in existing cryogenic systems.…”

ESR micro-imaging of LiNc-BuO crystals in PDMS: Spatial and spectral grain distribution

“…It is based on the pulsed ESR microscopy imaging probe described in details in [13] with some modifications in the gradient coil configuration and their cooling methodology. Thus, while the gradient coils geometry is identical to the one described in [13], each individual coil in a gradient-coil-pair is driven separately and therefore has different properties with respect to the gradient drivers.…”

“…It is based on the pulsed ESR microscopy imaging probe described in details in [13] with some modifications in the gradient coil configuration and their cooling methodology. Thus, while the gradient coils geometry is identical to the one described in [13], each individual coil in a gradient-coil-pair is driven separately and therefore has different properties with respect to the gradient drivers. For example, each of the two X-gradient coils (based on Maxwell pair geometry) is exhibiting an inductance of 2.2 lH, a resistance of 1 X, and produces magnetic field gradient of 2.74 T/mÁA (calculated via the method described in ref [14], assuming the coil counterpart is also fed by the same current magnitude).…”

Single-Particle Phenomena in Magnetic Nanostructures

“…47. Twig et al [256,257] report on the enhanced sensitivity for EPR measurements using a surface loop-gap microresonator, which reduces the effective volume of the resonator, though has a low Q factor of around 15. The system operates in the frequency range 6-18 GHz at room temperature and has the capability for measurements down to 5 K. Furthermore, it offers a sensitivity of 1 Â 10 6 spins/ ffiffiffiffiffiffi ffi Hz p , corresponding to around $ 2.5 Â 10 4 spins for a 1-h measurement.…”