Regensburg 2004 – wissenschaftliches Programm

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MA: Magnetismus

MA 15: Magnetische dünne Schichten I

MA 15.9: Vortrag

Mittwoch, 10. März 2004, 17:15–17:30, H10

Magnetic microstructure of granular epitaxial NdFeB films — •V. Neu, S. Melcher, U. Hannemann, and S. Fähler — IFW Dresden, Helmholtzstr. 20, 01069 Dresden

Epitaxial NdFeB films combine a perfect alignment of the easy magnetic axis perpendicular to the substrate with a high coercivity up to 2 T [1]. They possess high nucleation fields and the coercivity is mainly limited by local stray fields. Furthermore they grow in isolated, rectangular grains, which makes these films an ideal system to locally study the magnetic domains of a self-organized microstructure.

In this paper we used Magnetic Force Microscopy (MFM) and global magnetization measurements to examine a series of Nd-rich NdFeB films deposited at different temperatures. At deposition temperatures around 545^∘C the films neither have a perfect degree of texture nor do they switch homogeneously. The microstructure consists of a small grained film of NdFeB with the Nd-rich phase segregated as large spherical grains. At the optimum temperature of 630^∘C uniform switching occurs and a coercivity of 2 T is obtained. These films consist of rectangular, µm-sized NdFeB grains, which show typical stripe domains with an average width of 150 nm. At higher temperatures (670^∘C) the grain size distribution broadens significantly. This is reflected in a less uniform switching behavior, which is observed with global and local measurement techniques.

[1] U. Hannemann, S. Fähler, V. Neu, B. Holzapfel, L. Schultz, Appl. Phys. Lett. 82, 3710 (2003)