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Nuclear magnetic resonance microscopy at an isotropic resolution of 3.0 lm was realized by using dedicated hardware such as RF surface microcoils, a planar triple-axis gradient with 6,500 G/cm, and a static magnetic field of 18.8 T. Purely phaseencoded constant time imaging was used to allow increasing the gradient strength for the suppression of diffusion effects without reducing the signal-to-noise ratio. For this method the relationship between gradient strength and true spatial resolution was investigated, and an empirical formula is provided that is useful for practical applications. The characteristics of the different hardware components were investigated experimentally. Furthermore, microscopic phantom images were acquired and evaluated for their true resolution. It is demonstrated that the use of sufficiently large gradients enables suppressing diffusion-related loss of spatial resolution.

We describe the fabrication and the performance of a microcoil-based probe for electron spin resonance (ESR) spectroscopy on micrometer sized samples. The probe consists of a 100 μm planar microcoil fabricated on a glass substrate, tuned and matched at 1.4 GHz (L band) using miniaturized ceramic capacitors. We performed continuous wave ESR experiments on samples having a volume between (100 μm)3 and (10 μm)3. At 300 K, we achieved a spin sensitivity of about 1010 spins/G Hz1/2, which is comparable to that of commercial ESR spectrometers operating at 9 GHz (X band). The results reported in this article suggest that microcoil-based probes might represent a valid alternative to conventional microwave cavities for ESR studies of sample of the order of (100 μm)3 and smaller.

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