Field averaging effect and estimation of minimum sample size in wide-field diamond microscopy

Wide-field diamond microscopy is a powerful imaging method based on diamond nitrogen-vacancy (NV) centers. It enables magnetic imaging over wide areas of sample with fast data acquisition. However, there can exist field averaging effect resulting from the large field gradient around magnetic samples and the collective measurement with ensemble NV centers in a diffraction-limited laser spot. As a result, the overall magnitude of magnetic fields is greatly reduced compared to the actual fields. Here, we conduct micromagnetic simulation on different sizes of magnetic samples with various spatial resolutions. We find that based on the magnetic sensitivity and the spatial resolution of a wide-field diamond microscope, one can estimate the minimum size of sample resolvable with the setup. This provides useful information in the design of an experiment without unnecessary trial and error measurements.