Positive Domain-Wall Magnetoresistance of Ferromagnetic Point Contacts

Presently, there is a strong interest in the domain-wall (DW) resistivity of ferromagnetic (FM) films, which is reported to be larger [1, 2] or smaller [3] than the domain resistivity. The magnitude of the effect is up to a few percent. Typically, in an experiment an external magnetic field H is swept from a high value, where the film is single-domain, through zero field, where DWs exist. The DW resistivity is extracted from the magnetoresistance (MR). The DW magnetoresistance (DWMR) has a maximum (DWs increase resistance) or a minimum (DWs decrease resistance) around H = 0. So far, mainly samples with many DWs were studied. Here, we use FM nanoconstrictions or point contacts for the DW problem. These are designed to catch a single DW at the constriction (see Fig. 1), so that they are expected to show a DWMR extremum between the coercive field of the electrodes.