title: 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.
authors.affiliation: Instituto de Ciencia de Materiales de Aragón (ICMA), Departamento de Física de la Materia Condensada, Universidad de Zaragoza-CSIC, Pedro Cerbuna 12, Zaragoza, Spain. af457@cam.ac.uk
authors.forename: A
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authors.lastname: Fernández-Pacheco
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authors.initials: KW
authors.lastname: Chou
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authors.lastname: Córdoba
authors.forename: A
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authors.lastname: Szkudlarek
authors.forename: L O'
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authors.forename: Cz
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authors.lastname: Kapusta
authors.forename: M R
authors.initials: MR
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authors.forename: J M
authors.initials: JM
authors.lastname: De Teresa