MFM of vortices in Niobium single crystal

 

These MFM measurements were taken on a Niobium single crystal at various temperatures below the critical temperature of Nb (9.3 K). In the sequence of four smaller images on the right , vortices can be clearly seen in various cooling fields. The topographic features circled in red show that the images are taken at the same area. The green arrow indicates a vortex that disappeared between consecutive scans.