Dresden 2011 – scientific programme

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MA: Fachverband Magnetismus

MA 13: Magnetic Materials II

MA 13.3: Talk

Monday, March 14, 2011, 17:30–17:45, HSZ 401

Switching processes and thermal activation in a hard magnetic FePt film — •Christian Behler, Volker Neu, Ludwig Schultz, and Sebastian Fähler — IFW Dresden, P.O. Box 270116, D-01171 Dresden, Germany

In order to understand the switching behaviour of a granular FePt film we examined the angular dependence of the switching field and studied the thermal activation of the switching process via magnetisation relaxation measurements. The investigated film with a nominal thickness of 5  nm is grown epitaxially in L1₀-ordered structure. The coercive field, measured parallel to the easy axis, reaches a value of 7.4 T, which is about 70 % of the anisotropy field (10.8 T). The angular dependent switching field is in good agreement with the Stoner-Wohlfarth-Model when the above observed reduction in coercivity is included. We conclude that the switching behaviour approaches Stoner-Wohlfarth, but the nucleation starts at defects with reduced magnetic anisotropy. This result is supported by the size of the activation volume, which was determined from viscosity measurements. Compared with the grain volume the smaller activation volume also indicates that the switching process is initiated by inhomogeneous domain nucleation.