Nanostructures defined by the local oxidation of the ferromagnetic GaMnAs layer

The results of local anodic oxidation (LAO) on the thin GaMnAs layers are reported. The ferromagnetic GaMnAs layers were prepared by low-temperature molecular beam epitaxy (MBE) growth in a Veeco Mod Gen II machine. The LAO process was performed with the atomic force microscope (AFM) Smena NT-MDT placed in the sealed box with the controlled humidity in the range 45-80%. The oxide was grown in the semi-contact mode of the AFM. The sample was positively biased with respect to the AFM tip with the bias from 6 to 24V. The conductive diamond-coated AFM tips with the radius 30nm were utilized for the oxidation. The tip speed during the oxidation was changed from 400nm/s to 1.5@mm/s. The tip force was also changed during the oxidation. The height of oxide nanolines increases with applied voltage from 3 to 18nm. The width of these lines was approximately 100nm at half-maximum. The magnetoresistance measurements of the sample with 1D lateral constriction by the LAO and the micromagnetic simulations of the structure with two lateral constrictions are presented.