The physical basis that underlies a preferred magnetic moment orientation in magnetic thin films can be quite different from that observed in bulk materials. The presence of an interfacial structure in a multilayered stack is the basic ingredient for this changeover. By varying the thickness of the individual layer and choosing appropriate materials, it is possible to tailor the magnetic anisotropy in thin films. The most dramatic manifestation in this regard is the change of the preferential direction or the easy axis of the magnetization from the commonly observed in-plane orientation to the perpendicular direction. This phenomenon is usually referred to as perpendicular magnetic anisotropy (PMA). In this chapter we have reviewed PMA in thin films; the theory of magnetic anisotropy and crystallographic, structural (strain), and interfacial contributions to PMA. It is important that the films retain the PMA on thermal annealing if they are to be used in device applications. The main reason for the reduction in PMA on annealing is intermixing at the interface, and therefore, the ways to avoid or reduce this intermixing upon annealing are discussed. We have also incorporated the applications of thin films with PMA in magnetic recording and magnetic tunnel junctions with PMA (p-MTJ) at the end of the chapter. © 2017 by Taylor & Francis Group, LLC.
|Journal||Advances in Magnetic Materials: Processing, Properties, and Performance|