Effect of the quantum domain wall on conductance quantization and magnetoresistance in magnetic point contacts

The electron transport through a magnetic point contact is studied with special attention to the effect of an atomic scale domain wall. When the magnetizations of left and light electrodes are antiparallel, the atomic scale domain wall is created inside the contact. We show that the spin precession of conduction electron is forbidden in such an atomic scale domain wall and the sequence of quantized conductances differs from that of the single domain point contact. We also show that the magnetoresistance is strongly enhanced for the narrow point contact and oscillates with the conductance.