Positive domain wall resistance in atomic-sized constrictions

Abstract

The magnetoresistance of a domain wall (DWR) is measured in Permalloy constrictions down to a few atoms in size. We find a negative DWR for nanometer-sized constrictions, becoming positive in the atomic-contact regime. We conclude that the contribution from the anisotropic magnetoresistance (AMR) is gradually weakened as size decreases and spinpolarized transport across an atomically narrow constriction dominates the magnetoresistance. This is revealed by a positive contribution to the DWR reaching four percent for the smallest constrictions, which depends significantly on the specifics of the atomic arrangement.

Domain-Wall Induced Large Magnetoresistance Effects at Zero Applied Field in Ballistic Nanocontacts

“…In agreement with Ref. 24, our data shows that we can also exclude AMR since neither the angle-dependence nor the sign of the MR signal in our R(α) measurements agrees with the characteristics of large AMR as sometimes observed in nanocontacts [27] (also see Fig. 1 in supplementary material [23]).…”

“…2(a)) and we observe positive and negative MR. This large MR effect completely supersedes the small AMR [24] and dominates the overall MR.…”

“…Refs. [6][7][8][24][25][26]), here the magnetization of the arms can be switched in low fields, independently of the precise geometry of the constriction, resulting in distinct stable configurations that can be probed at zero field. This means that we can uniquely identify the presence of a DW and the resulting impact on the MR even at zero field, as depicted in Fig.…”

Electrical detection of internal dynamical properties of domain walls

“…Such a curve opening in the magnetoresistance often indicates the appearance of an inhomogeneous magnetic state. In the particular case of our structure with an almost transverse applied field, it corresponds to the nucleation of a domain wall in the notch area [14,15]. The presence of the DW increases the total stripe resistance by around 0.6 .…”

Nanoscale Chemical and Structural Characterization of Transient Metallic Nanowires using Aberration-Corrected STEM-EELS

“…This material was chosen for demonstration because the structure and chemistry of their nanojunctions can potentially strongly influence their magnetic and transport properties. 16 Their structure and chemical composition were studied dynamically by bright-field (BF), high-angle annular dark-field (HAADF) and spatially resolved EELS. We show (a) direct, real-space proof of the existence of magnetic alloy down to atomic-scale contacts, (b) that the chemical compositions of the alloy nanowires are rather homogeneous even down to 1 nm diameter, essentially retaining the nominal bulk composition, (c) that the surface of the thick wire (∼ 6 nm) is slightly enriched in Fe, (d) that the permalloy atomic scale junctions could be in an oxidized state, and (e) that any adsorbed amorphous carbon contamination layer could be totally removed by electron irradiation.…”