Size effect of the domain-wall magnetoreristance in TbFeCo wires

We studied the domain-wall (DW)-induced magnetoresistance (MR) effect in TbFeCo wires with a thickness of 18 nm and different widths at room temperature. In wide (up to 10-µm-width) wires, small MR values that weakly depended on the number of DWs inside the wires, were obtained. This could be attributed to multi-domain structures that reduced the spin asymmetry in the wire. For all wires, the MR values strongly depended on the bias current. In a narrow (0.8-µm-width) wire with a single DW structure, large MR values of up to 8% were observed at a low bias current and depended on the DW structure inside the TbFeCo wires. On the other hand, the MR values were greatly reduced at large bias currents, which induced magnon and phonon scattering effects. The contribution of the single DW resistivity to the MR effect was found to be large for a narrow wire due to the large spin asymmetry of conduction electrons through the DWs. The well-defined and controllable number of DWs inside magnetic wires is expected to obtain high and multi-level MR values as well as high potentials for future magnetic devices.