Nonreciprocal differential detection method for scanning Kerr-effect microscopy

We describe an optical detection scheme for scanning Kerr-effect microscopy (SKEM) which does not require modification of the magnetic state of a sample for domain observation. The scheme exploits the nonreciprocal nature of the magneto-optic Kerr effect (MOKE) to distinguish polarization rotation due to sample magnetization from other spurious sources, such as sample roughness and birefringence of the microscope optics. We present SKEM images of domain structures in lithographically patterned Ni81Fe19 elements which demonstrate the imaging capabilities of the new detection scheme for materials with typical MOKE magnitudes.