Dynamic interface formation in magnetic thin film heterostructures.

Magnetic thin film heterostructures have been widely studied for fundamental interests in the emergence of novel phenomena accompanied by the heterointerface formation as well as their promising practical potential. Combining x-ray magnetic circular dichroism with scanning tunneling microscopy, we show for Mn/Fe thin film heterostructures that the interfacial factors dominating electronic and magnetic properties of the entire system dynamically change with the amount of the Mn overlayer. Element specific magnetization curves of the Fe layer exhibit a two-step spin reorientation transition from out-of-plane to in-plane direction with increasing the Mn coverage. Atomic-scale characterizations of structural and electronic properties in combination with the first-principles calculations successfully unravel the roles of the entangled interfacial factors, and clarify the driving forces of the transition. The first step of the transition at a low Mn coverage is dominantly induced by the formation of FeMn disordered alloy at the heterointerface, and the electronic hybridization with interfacial FeMn ordered alloy is dominant as the origin of the second step of the transition at a high Mn coverage.