Sample drift
Thermal instability or strong magnetic forces on the sample may lead to sample motion and drift. In the difference image mode the sample positions for life- and background image may then not coincide anymore, leading to strong contrast features around defects and edges in the difference image. By shifting the sample back to the same position as for the background image, such non-magnetic contrast features can be suppressed. This applies to both, in-plane drifts as well as out-of-plane drifts (defocusing).
Drift correction
The drift correction is realised by xyz-piezo stages and real-time software feedback control. Piezo stages with sub-nanometer resolution are available for the regular sample holder of the xyphi stage, for the sample stage of the perpendicular electromagnet and for the cryostat and heating stage.
Here, the Permalloy patterned film element, with a side length of 70 µm, was displaced from the position where the reference background image was captured. This displacement induced a strong contrast highlighting sample defects in the live image. After activating the stabilization, the sample was returned to its original position, effectively suppressing all non-magnetic contrast features
Utilizing this procedure, magnetic domains can be investigated even on samples with complex topography or with high roughness.
The resolution limit of the Kerr microscopy is further addressed in Relevant technical publications and in the following paper:
Size analysis of sub-resolution objects by Kerr microscopy (I. Soldatov, W. Jiang, S.G.E. Te Velthuis, A. Hoffmann and R. Schäfer, Appl. Phys. Lett. 112 (26), 262404 (2018))