Domain wall resistance in (Co/Pt)10-nanowires

– The clear separation of the domain wall magnetoresistance from the anisotropic magnetoresistance has been successfully achieved by investigating the transversal magnetoresistance of individual (Co/Pt)10-nanowires. Since the magnetic easy axis of this nanowires is out of plane, the magnetization is always perpendicular to the current direction when applying a magnetic field transversally. Most importantly, even the domain walls do not give rise to an anisotropic resistance contribution by themselves under these conditions, and thus the pure domain wall magnetoresistance can be measured. The interpretation of the resistance behavior is confirmed by Monte Carlo simulations giving the magnetization distribution during the magnetization reversal process. It can be shown that the observed resistance behavior reflects the dependence of the domain wall magnetoresistance on the domain wall structure. Introduction. – Since the experiments on iron whiskers showed that domain walls in a ferromagnet give rise to a positive resistance contribution [1], the effect of domain walls on the transport properties of ferromagnetic thin films and nanostructures became a topic of great interest. The first direct observation of the domain wall magnetoresistance (DWMR) was obtained by Gregg et al. [2]. They proposed that the positive resistance contribution of the domain walls is due to a combination of two effects: 1) The coincidence of the precessional behavior of the spins of the conduction electrons with the local variation of the exchange field while passing through the domain wall. 2) Spin-dependent scattering in the domain walls causing a mixture of majority and minority spins as has been described for the giant magnetoresistance (GMR) effect. This positive DWMR was theoretically explained [3,4] and observed in various experiments [5–8]. However, other experiments reveal negative domain wall resistance contributions [9,10] which have been explained by de-phasing effects in domain walls [11]. Up to now, a controversial discussion on whether the DWMR is positive or negative is still present even though recent investigations point out that the negative DWMR effect is mainly due to the anisotropic magnetoresistance of the domain wall itself [12]. The main difficulty in measuring the DWMR is that in most systems it is superposed by a strong anisotropic