Principle
evico magnetics Kerr microscopes can be used to measure the (surface) magnetization vector field of soft magnetic specimens in a quantitative way.
To do so, one has to calibrate the contrast by measuring the Kerr intensity in the saturated sample state in all direction. This has to be done at longitudinal and transverse sensitivities, leading to phase-shifted sensitivity functions. Then the Kerr intensity of an unknown domain can be compared with both sensitivity functions, leading to a unique magnetization vector.
Experiment
By combining those two images with complimentary sensitivity directions, the true magnetization distribution can be reconstracted.
The vector field can then be plotted using a colour code or vector plots (like in micromagnetic simulations).
Dynamics
Also complete magnetization processes can be quantitatively be measured.
Sample is a Permalloy patterened film element with thickness of 240 nm and a side size of 70 um subjected to slowly cahnging magnetic field.
The further information on quantitative Kerr microscopy can be found in the following papers (also aviabale in Relevant technical publications as preprints):
Advances in quantitative Kerr microscopy (I. V. Soldatov and R. Schäfer, Phys. Rev. B 95, 014426 (2017))