Semiconductor-based magnetic materials offer new possibilities for the integrating electronic and magnetoelectronic devices providing a basis for future spin electronics.

In the present study we fabricated and investigated a simple magnetoresistive nanodevice formed by a narrow constriction in the epitaxial film of a ferromagnetic semiconductor (Ga,Mn)As. We performed experiments on 50 nm thick film of Ga_0.99Mn_0.01As grown by the low-temperature molecular beam epitaxy on semi-insulating GaAs substrate. Magnetic properties of the film, which exhibits metallic-type hole conductivity, were measured by means of SQUID magnetometer showing the Curie temperature of 50 K. We fabricated constrictions of submicron width in the film by a method of the electron-beam-lithography patterning and oxygen ion implantation [1]. Individual devices containing the constriction with lithographic width of 400 nm and supplied with two Ohmic contacts were subjected to magnetotransport measurements at temperatures down to 1.5 K and the magnetic field up to 13 T. At the lowest temperatures both the constricted devices and the non-constricted reference samples exhibit a large positive magneto-conductance, which can be described by the suppression of weak localization of holes by the external magnetic field. Characteristic features revealed in the magneto-conductance of the constricted devices are abrupt jumps of an enhanced conductance that appear when the sweeping magnetic field crossed the regions of the coercive field of the film. We interpret these features as resulting from the erasing of weak localization by a magnetic domain wall nucleated in the constriction.

[1] T. Figielski, T. Wosiński, A. Morawski, O. Pelya, J. Sadowski, A.L. Tóth, and J. Jagielski, Phys. Stat. Sol. (a) 195, 228 (2003).