Direct observation of magnetic exchange-spring development in epitaxial DyFe2/YFe2superlattices by magneto-optical Kerr effect

The magnetic reversal properties of molecular beam epitaxy (MBE) grown Laves phase single crystal YFe2-dominated DYFe2/YFe2superlattices were investigated using magneto-optical Kerr effect (MOKE) measurements. Single crystal DYFe2/YFe2superlattices with a thickness ratio of 1:4 were MBE-grown with a (110) growth direction. In the epitaxial superlattices, the development of exchange-spring structure during magnetic reversal is revealed by both magneto-optical reflectivity and Kerr rotation angle loops. The bending fields of the samples are found to be close due to nonideal anisotropy in both hard and soft layers. For the sample with thin soft/hard layers, large magneto-optical reflectivity change up to 0.25% was observed. This can be related with rotation of Fespins in YFe2soft layers under a low pinning field, in consistence with the small switching field of thin DYFe2hard layers measured experimentally.