L. Däweritz, F. Schippan, K.H. Ploog

B. Dennis, K.-H. Neumann, K.R.A. Ziebeck

Thin ferromagnetic MnAs films of excellent structural integrity were grown by molecular beam epitaxy on GaAs(001) substrates. The correlation between the topography of the MnAs film and its magnetic domain structure has been studied by systematic in-plane and out-of-plane magnetization measurements and by magnetic force microscopy (MFM).

Exact control of the GaAs(001)-c(4 ´ 4) template and the MnAs growth procedure allows to prepare structurally single-domain films. The exposed MnAs() surface with the [0001] direction of NiAs-type MnAs parallel to GaAs develops stoichiometry-dependent reconstructions. Annealing at moderate temperatures improves the surface quality considerably. For MnAs growth on such surfaces RHEED intensity oscillations are recorded, evidencing layer-by-layer growth.

Magnetization measurements show a high anisotropy of the ferromagnetic films. The results of combined magnetization, MFM and AFM measurements can be summarized as follows:

(i) Magnetic moments in the domain wall along the easy axis of magnetization are out-of-plane, i.e. the domain walls are of 180 ° Bloch type.

(ii) External magnetic fields change the magnetic structure of the MnAs films completely.

(iii) Changes in the domain structure occur on a length scale of 1 micron.

(iv) The magnetization pattern directly reveals the correlation between magnetic and structural topography with grooves along [0001] (perpendicular to the magnetic domain walls).