Dresden 2011 – wissenschaftliches Programm
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MA: Fachverband Magnetismus
MA 45: Micromagnetism/ Computational Magnetics
MA 45.1: Vortrag
Mittwoch, 16. März 2011, 17:30–17:45, HSZ 403
Pinning of domain walls in exchange-spring composite media — •Dagmar Goll1 and Helmut Kronmüller2 — 1Aalen University, Materials Research Institute, Beethovenstr. 1, 73430 Aalen — 2Max Planck Institute for Metals Research, Heisenbergstr. 3, 70569 Stuttgart
High-density magnetic recording in the Tbit/in2 range is based on single bit particles in the nm-range. The prerequisites for high-density recording are the following ones: Texture axis in perpendicular direction, thermal stability up to 100 ∘C, reversal fields between 1 - 2 T, and switching times in the ps-range. Composite nanoparticles composed of a soft and a hard magnetic layer are suitable to fulfill the above conditions. The magnetic ground states of bi- and trilayers are determined as a function of the thickness of the soft magnetic layer. It is shown that there exist critical fields for the ground state defining homogeneous and inclined magnetic states as well as reversal fields depending on the exchange length of the hard magnetic layer. The coercive field has a lower bound for film thicknesses larger than the exchange length of the magnetization determined by the depinning field of a Néel wall at the phase boundary. An upper limit exists for film thicknesses of the soft magnetic film of the order of the exchange length of the crystalline anisotropy of the hard magnetic phase and is given approximately by 1/4 of the nucleation field of the hard phase.