Room-temperature ferromagnetism in Ge1-xMnx nanowires

We report an observation of room temperature ferromagnetism in Ge nanowires doped with Mn. High-density arrays of Ge1-xMnx(x=1%-5%) nanowires with the smallest diameter of 35 nm have been synthesized within the pores of anodized aluminium oxide membranes using a supercritical fluid inclusion-phase technique. Structural analysis of the nanowires proved the existence of a highly crystalline germanium host lattice containing discrete manganese atoms. All of the nanowires studied displayed ferromagnetic properties at room temperature. Ferromagnetic ordering reaches a maximum at intermediate Mn concentrations. The magnetic properties of the nanowires can be understood by considering the influence of co-dopant nonmagnetic impurities and nanowire/membrane interfaces.