Regensburg 2010 – scientific programme

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KR: Fachverband Kristallographie

KR 10: Poster: Multiferroics (with MA, DF, KR, DS)

KR 10.48: Poster

Tuesday, March 23, 2010, 10:45–13:45, Poster A

Transition from shape anisotropy to magnetocrystalline anisotropy in ultrathin FePt films — •Karin Leistner, Juliane Wunderwald, Sebastian Fähler, and Ludwig Schultz — IFW Dresden, Dresden, Germany

FePt films have recently attracted great interest as possible media for perpendicular magnetic recording, but also for fundamental studies of magnetism in reduced dimensions. As FePt it is very corrosion resistant it is ideal for ultrathin films, however, L10 ordering and thus high magnetocrystalline anisotropy are harder to achieve at small particle size. In the present study, 2 nm thick FePt films have been deposited by pulsed laser deposition on MgO(001) with a Cr/Pt buffer. The magnetic properties have been obtained by Hall measurements and measurements of the Kerr rotation. Without post annealing, the out-of-plane (op) hysteresis is controlled by shape anisotropy with an anisotropy field of 1.4 T. The easy axis lies in-plane and in the op hysteresis curve rotation of magnetization is observed. This is as expected for smooth ultrathin disordered FePt films. When post annealing is applied, a continuous decrease of the effective in-plane anisotropy field is observed with increased annealing time. After a post annealing time of 15 min, the easy axis lies op and the op hysteresis shows switching of magnetization and a larger coercivity. The reason is that ordering in the (001)-textured films leads to an increased magnetocrystalline anisotropy in the op direction that competes with shape anisotropy. Thus, in these ultrathin FePt films anisotropy can be continuously adjusted from pure shape anisotropy to magnetocrystalline anisotropy.