Mapping the domain wall pinning profile by stochastic imaging reconstruction

Polar magneto-optical Kerr effect microscopy and subsequent stochastic imaging reconstruction have been used to map out the distinct pinning profiles of randomly distributed intrinsic defects (pointlike/linelike), as well as their dependence on the external magnetic field in 2-μm-thick yttrium iron garnet films. A comparison of the pinning profiles produced by these intrinsic defects and the extrinsic defects (made by focused ion beam lithography) has also been made. In addition, we have found a linear dependence of the pinning potentials on the depths of the fabricated pointlike defects. Our observations should provide a fundamental understanding of the role of defects in domain wall spintronics.