Nonlinear transport below T_C for lateral nanoconstrictions realized in a 100 nm GaMnAs epifilm

Electrical transport across lateral geometrical nanoconstrictions realized in 100 nm thick GaMnAs epifilms is studied. The constrictions are patterned with the aid of chemical etching techniques, as opposed to plasma-assisted methods. Transport behavior across the constrictions, where domain walls can be formed and pinned, changes from Ohmic to non-Ohmic below temperatures corresponding to epifilm TC for junctions with high resistances. Magnetoresistance measurements across such junctions qualitatively show similar behavior to unpatterned epifilms attributable to anisotropic magnetoresistance. The experimental IV curves are in good agreement with theoretical models accounting for spin flop across a region of high resistance.