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AM: Magnetismus
AM 15: Mikromagnetismus I (Magnetisierungsprozesse und Dom
änenstrukturen)
AM 15.6: Talk
Thursday, March 29, 2001, 16:15–16:30, S 5.4
Tailoring magnetic properties by varying size and shape of ferromagnetic dots — •S. A. Nepijko1, U. Muschiol2, A. Oelsner1, O. Schmidt1, M. Klais1, O. de Haas2, C. M. Schneider2, and G. Schönhense1 — 1Johannes Gutenberg-Universität Mainz — 2Institut für Festkörper- und Werkstofforschung Dresden
The domain structure of permalloy/NiO/permalloy systems was investigated by magnetic circular dichroism using a PEEM. The circularly polarised light of 708 eV (energy of the absorption L3-edge for Fe) was used for the excitation. Measurements were carried out at the 4.2 R beamline in Trieste and at the ID UE56/1 of BESSY II. The upper permalloy film of the samples was nano-structured by ion etching. We varied the size and shape of the investigated structures particularly to study how this parameters influence the formation of magnetic domains. The pattern elements (lateral dimensions ranging from 24 nm down to 0.4 nm) have been in the shape of rectangle/ellipse/rhombus with the sides/axes/diagonals ratio a:b between 1:1 and 1:10. The number of domains decreases, if one reduces the lateral particles sizes proportionally (a/b=const). However, by leaving one dimension constant (a=const) and reducing just b, a non-monotonic change for the number of domains is observed with reversal magnetisation orientated along the long side/axis/diagonal. This indicates, that the same permalloy particles contain different numbers of domains depending on the direction of the reversal magnetisation, i.e. the magnetic stiffness is correlated to the reversal magnetisation direction. Thus we can efficiently tune the magnetic stiffness by changing the shape (ratio a/b) of the structured particles.