Observation of hysteretic magnetoresistance in Mn-doped GaN nanowires with the mesoscopic Co and TiAu contacts

We have studied the spin dependent tunneling properties of Mn-doped GaN nanowires with ferromagnetic Co contacts. The magnetoresistances were measured between two ferromagnetic Co electrodes, or Co and TiAu electrodes through Mn-doped GaN nanowires. The magnetoresistances of nanowire with the Co electrode indicate hysteretic behaviors, which are commonly observed in tunnel magnetoresistance devices. The magnetoresistance ratio increases from -0.6% at 20 K to -9.4% at 1.74 K. It is believed that the hysteretic magnetoresistances originate from the tunnel magnetoresistance effect between the ferromagnetic phases of nanowire and Co electrode.