Reorientation transitions and spin-canted phases at the interferences of transition-metal films

Magnetic nanostructures involving transition metals (TMs) are the focus of an intense research activity that is driven to a large extent by the quest for new materials with specific applications. Ultrathin films with stable perpendicular magnetization, one of the major early discoveries in this field, remain a subject of central interest from both fundamental and technological standpoints. A particularly relevant example of tailoring the magnetic behavior at the nanoscale is the experimental observation that magnetization-reorientation transitions can be induced by modifying the interfaces, for example, by capping magnetic films with nonmagnetic elements. Understanding and controlling these phenomena at an atomic level are central issues in current research on magnetism with considerable implications for the development of magnetic nanostructures at surfaces.

The magneto-anisotropic properties of Co thin films on Pd and Pt surfaces have been analyzed from a local perspective in the framework of a self-consistent tight- binding theory. Layer-resolved electronic calculations of the magnetic anisotropy energy (MAE) provide new insights to the off-plane magnetization observed in Pd capped Co films on Pd(111). Remarkable magnetization-reorientation transitions have been determined as a function of film thickness and capping element. The existence of an intermediate spin- canted phase between perpendicular and in-plane phases has been theoretically demonstrated. The relevant interface magnetic anisotropies responsible for the experimentally observed off-plane magnetizations have been identified. A detailed microscopic analysis reveals that the Co-Pd interfaces present a remarkable internal magnetic structure with the Pd and Pt contributions playing a dominant role. Besides the interest of these specific systems, the present local approach opens the way to novel investigations of magneto-anisotropic effects on a variety of more complex 3d/4d and 3d/ nanostructures at surfaces.

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