Conductance quantization in magnetic and nonmagnetic metallic nanowires

Transport properties of ferromagnetic quantum wires at room temperature are not yet fully understood, and the role of electronic structure of magnetic atoms in the conductance quantization is still under discussion. We present experimental results on the conductance quantization in point contacts between ferromagnetic (Co) or nonmagnetic (Au) wires and semiconductor (Ge) samples. The main features of the conductance histograms for the nonmagnetic wires are consistent with the conductance quantization in the units of quantum conductance G0 = 2e2/h. For the ferromagnetic Co nanowires, the conductance shows plateaus at nG0, generally with non-integer n. Such behaviour is a consequence of the complex electronic structure of magnetic 3d transition-metal atoms. A description of the quantization phenomena is presented in terms of the Landauer formalism for the current flowing through a small nanoconstriction.