Tweaking magnetic anisotropy beyond the monolayer limit : low energy electron microscopy studies on spin-reorientation transitions on Co/Ru
Magnetic anisotropy of a thin film is the result of a delicate balance of many contributions. In particular, the Co/Ru(0001) systems presents consecutive spin-reorientation transitions as a function of thickness: monolayer thick films are magnetized in-plane in remanence, while bilayer islands and films present an out-of-plane magnetization. Films three atoms thick are again magnetized in-plane. These observations imply that the magnetic anisotropy energy changes sign at each consecutive layer. But this sensitivity to both thickness and, presumably, to adsorbates implies that local techniques capable of determining both structure and magnetic properties are required. In this work we will use both spin and non-spin polarized low energy electron microscopies (LEEM) together with photoemission microscopy (PEEM).
We will present results that show how the magnetic anisotropy can be further changed by deposition of metals and non-metals. In particular, the deposition of several metals has been found to again cause consecutive spin-reorientation transitions. Other adsorbates such as hydrogen are also capable of producing spin-reorientations. Furthermore, deposition of hydrogen not only changes the magnetic anisotropy energy sign, but controlling the coverage can change in a controlled way the magnetic anisotropy as observed in real-time by the evolution of the magnetic domain patterns of the film. We will complement the experimental observations with first-principles calculations.