Thin films MnGe grown on Si(111)

MnGe has been grown as a thin film on Si(111) substrates by molecular beam epitaxy. A 10 \AA\ layer of MnSi was used as seedlayer in order to establish the B20 crystal structure. Films of a thickness between 45 and 135 \AA\ have been prepared and structually characterized by RHEED, AFM and XRD. These techniques give evidence that MnGe forms in the cubic B20 crystal structure as islands exhibiting a very smooth surface. The islands become larger with increasing film thickness. A magnetic characterization reveals that the ordering temperature of MnGe thin films is enhanced compared to bulk material. The properties of the helical magnetic structure obtained from magnetization and magnetoresistivity measurements are compared with films of the related compound MnSi. The much larger Dzyaloshinskii-Moriya interaction in MnGe results in a higher rigidness of the spin helix.