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MA: Magnetismus

MA 20: Magnetische dünne Schichten II

MA 20.1: Vortrag

Donnerstag, 11. März 2004, 10:15–10:30, H10

Magnetic properties of cobalt thin films grown on Ni₃Al(001) — •Stella Maris Van Eek, Ioan Costina, Vitali Podgurski, and René Franchy — Institut of Thin Films and Interfaces (ISG 3), Forschungszentrum Juelich GmbH, D 52425 Juelich, Germany

The growth and the magnetic properties of thin cobalt films on Ni₃Al(001) at 300 K were investigated using Auger spectroscopy, low energy electron diffraction, scanning tunneling microscopy and magneto optic Kerr effect (MOKE). Hysteresis loops of the Co layer were seen with MOKE in situ. The Co films were prepared with thicknesses from 1.8 ML to 8 ML and all were ferromagnetic at room temperature. The coercivity of the Co film increased with deposited material up to 5 ML and then decreased very slowly. We picked up a thickness of each one of these two regions: 3 ML and 7 ML to investigate the magnetic properties. At room temperature Co(001) grows fcc epitaxially due to the small misfit between the lattice constant of fcc-Co and Ni₃Al and forms two-dimensional islands. Annealing up to 700 K did not show interdiffusion but a coalescence and a flatening of the Co islands. The coercivity field increased with annealing at 700 K, for example the coercivity of the 7 ML Co sample showed an increase from 32(2) Oe to 43(2) Oe. For the 3 and 7 ML Co samples the evolution of the magnetic properties was investigated with the temperature. The magnetic ordering temperature values for the different thicknesses are reduced compared to the bulk one, this was explained with the scaling theory, which predicts a weakened magnetic order at the surface.