Correlation between the magnetic imaging of cobalt nanoconstrictions and their magnetoresistance response

Abstract

Scanning transmission x-ray microscopy (STXM) and magnetoresistance (MR) measurements are used to investigate the magnetic behavior of a nanoconstriction joining two micrometric electrodes (a pad and a wire). The reversal of the magnetization under variable external static magnetic fields is imaged. By means of a detailed analysis of the STXM images at the nanocontact area, the MR is calculated, based on diffusive anisotropic-MR. This MR agrees well with that obtained from electrical transport measurements, allowing a direct correlation between the MR signal and the magnetic reversal of the system. The magnetization behavior depends on the sample thickness and constriction dimensions. In 40 nm-thick samples, with 20 × 175 nm(2) contact areas, the magnetization at the two sides of the constriction forms a net angle of 90°, with a progressive evolution of the magnetization structure between the electrodes during switching. The MR in those cases has a more peaked shape than with 20 nm-thick electrodes and 10 × 80 nm(2) contact areas, where the magnetization forms 180° between them, with a wide domain wall pinned at the constriction. As a consequence of this configuration, a plateau in the MR is observed for about 20 Oe.

Optimized cobalt nanowires for domain wall manipulation imaged by in situ Lorentz microscopy

“…20 The FEBID spatial resolution is also very high, down to 3 nm in the case of Pt deposits, 21 so this technique is capable of producing nanostructures with very fine details such as constrictions, needle shape tips, etc. 22 In a recent work, high purity Co NWs of lateral size down to 30 nm were produced by FEBID. 20 Though the magnetic characterization of this type of systems has been carried out up to now by multiple indirect techniques, such as resistivity, magnetoresistance, Hall effect, magneto-optical Kerr effect, and electron microscopy, 19,20,[23][24][25] 26 MFM can however only give qualitative information on the nature of the DW appearing in these nanostructures.…”

“…19 The Co structures have been grown on electron-transparent 50-nm-thick Si 3 N 4 membranes, which are suitable for magnetic imaging in transmission experiments using electrons 20 or x-rays. 22 The lengths of the two branches of the NWs were fixed for all the objects to 3.5 lm and 8.5 lm for the short and long branches, respectively. The width (w) and the thickness (t) of the Co nanostructures have been varied through the array, w ¼ 125, 250, 500, 1000 nm and t ¼ 5, 8, 10, 13, 16, 19, 22, 25, 30 nm.…”

Present and future applications of magnetic nanostructures grown by FEBID

“…In ref. [36], we investigated the magnetic properties of structures as those shown in Fig. 4, consisting of two electrodes with different shapes: a square and a rectangle with pointed ends, joined by a constriction [36].…”

Coherent X-ray Imaging: Bridging the Gap between Atomic and Micro-scale Investigations

“…[50,58] Furthermore, magnetic domains can be imaged based on X-ray magnetic circular dichroism and their dynamics followed in pump-probe experiments. [48,59] Phase contrast is also possible, although absorption contrast is often more advantageous in the soft X-ray region of the spectrum where STXM experiments are commonly conducted. [41,60] With such diverse contrast mechanisms, STXM lends itself well to a wide range of investigations in almost every scientific discipline.…”