Mapping spatial and field dependence of magnetic domain memory by soft X-ray speckle metrology

J. Synchrotron Rad. (2012). 19, 293-306 (http://doi.org/hxv)

In thin ferromagnetic layers, microscopic magnetic domains tend to form. Often, the average size of these domains is well known, but their morphological changes throughout the magnetization loop are unclear. This work concentrates on magnetic domain memory, the ability of the material to retrieve the same domain morphology after field cycling. The memory is here induced in a Co/Pt multilayer via exchange coupling with an antiferromagnetic IrMn layer. We probe the memory with coherent X-ray magnetic scattering, a unique technique exploiting the magneto-optical contrast at resonance and the coherence of X-ray synchrotron radiation. The amount of memory is quantified by cross-correlation speckle patterns. The paper shows how to map out the memory at different spatial scales, with field and temperature dependencies.