Comparison of the magnetic properties of MnAs in bulk and epilayer samples.

J. MILANO, V. BODONGBO, L.B. STEREN, V. GARCIA, M. MARANGOLO, M. EDDRIEF, V.H. ETGENS, F. RIVADULLA.

S.C. de Bariloche

Conferencia; 13th International Conference on Solid Films and Surfaces.; 2006

Centro Atomico Bariloche

The magnetic properties of MnAs thin films are very different from those of the bulk. In particular, the bulk presents a magneto-crystalline transition at 313K. At this temperature, the ferromagnetic hexagonal low- temperature phase transforms into a non-magnetic orthorhombic one. However,  in MnAs  thin films these two phases coexist in a finite temperature range.                 In this work we present a study of the dependence of the phase coexistence on the thin film thickness and substrate orientation through magnetic measurements. A comparison of these results with those of the bulk compound will be  shown in our presentation. Magnetometric and ferromagnetic resonance experiments were performed on thin films of different thickness (66, 100 and 200 nm) grown over GaAs (111) and (100)  and into a powder sample. We observe that the coexistence region is independent of the film thickness when MnAs films are grown onto GaAs (111) but it depends on this parameter for films deposited on GaAs (100). The properties of samples of 200 nm thick  and larger are very similar to the bulk ones.