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Magnetoresistance of individual ferromagnetic GaAs/(Ga,Mn)As core-shell nanowires

We investigate, angle dependent, the magnetoresistance (MR) of individual self-assembled ferromagnetic GaAs/(Ga,Mn)As core-shell nanowires at cryogenic temperatures. The shape of the MR traces and the observed strong anisotropies in transport can be ascribed to the interplay of the negative magnetoresistance effect and a strong uniaxial anisotropy with the magnetic easy direction pointing along the wire axis. The magnetoresistance can be well described by a quantitative analysis based on the concept of the effective magnetic field, usually used to describe ferromagnetic resonance phenomena. The nanowires we investigate exhibit a uniaxial anisotropy which is approximately 5 times larger than the strain induced anisotropy observed in lithographically prepared (Ga,Mn)As stripes.