Magnetoresistance of nickel nanocontacts fabricated by different methods

Wei, He; Wang, T.-X.; Clifford, E.; Langford, R. M.; Han, Xiufeng; Coey, J. M. D.

doi:10.1063/1.2167061

Cited by 8 publications

(3 citation statements)

References 26 publications

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“…The conductance change under sweeping applied magnetic field is of the order of e 2 / h, even though the conductance varies by up to two orders of magnitude. When reaching resistance values corresponding to typical Sharvin's resistance in a metal (several ohms), the expected MR values do not exceed the per cent range, in agreement with experiments using point contact geometry [85,86,91].…”

Section: Magnetoresistance Propertiessupporting

confidence: 83%

Ballistic magnetoresistance?

Doudin

Viret

2008

J. Phys.: Condens. Matter

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We review the published work on electric transport in metallic magnetic nanocontacts of sizes reaching a single atom. Considering fabrication methods exempt from mechanical instabilities, we find two experimental consensuses in magnetoresistance measurements. Firstly, magnetoresistance does not exceed a few tens of per cent in atomic size constrictions. We attribute these modest values to the significant number of opened conduction channels expected in contacts of 3D metals. Secondly, anisotropic magnetoresistance is observed for all types of samples, with amplitudes at least one order of magnitude larger than those found in bulk samples. Abrupt resistance changes with field angle confirm the occurrence of discrete anisotropic magnetoresistance levels. The effect is attributed to enhanced spin-orbit coupling at the atomic scale, resulting in possible opening or closure of conductance channels when varying the angle between current and applied magnetic field.

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Section: Magnetoresistance Propertiessupporting

confidence: 83%

Ballistic magnetoresistance?

Doudin

Viret

2008

J. Phys.: Condens. Matter

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“…If the hole diameter and milling time/dose are chosen correctly (which is a function of the membrane thickness), the apex of the cone will just cut through the rear side of the membrane. 42 Generally, Si 3 N 4 membranes are used, but because charging can be an issue, SiC membranes 43 have also been used. The SiC membranes were coated with a metallic thin film to compensate for the intrinsic stress within the membranes.…”

Section: Fib Nanofabricationmentioning

confidence: 99%

Focused Ion Beam Micro- and Nanoengineering

Langford¹,

Nellen²,

Giérak³

et al. 2007

MRS Bull.

104

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This article is divided into four sections. The first section discusses FIB micro-and nanomilling and covers aspects such as pattern densities and milling threedimensional (3D) shapes. The second section covers FIB lithography, that is, Ga implantation or milling followed by a pattern transfer or growth step. The third section discusses FIB implantation for patterning and device fabrication. The fourth section highlights other fabrication techniques such as in situ micromanipulation. The article concludes with a discussion of possible future developments for enhancing the nanofabrication capabilities of FIB systems. FIB Micro-and NanomillingFIB milling, whether for sample preparation for electron microscopy or direct maskless patterning, is the most commonly used application of the systems and has been used to prepare a range of devices including lenses on the ends of fibers, 6 pseudo spin valves, 7 pillar microcavities, 8 and stacked Josephson junctions. 9 The smallest ion beam spot size is approximately 5-10 nm, which enables correspondingly small features to be patterned. The shape of an FIB cut is dependent on many factors, such as its geometry, milled depth, ion beam profile, and the redeposition of sputtered material. (Other factors, such as self-focusing, are discussed in the section "Micromachining 3D Structures with Complicated Shapes"). The combination of ion beam profile effects and sputter yield changes with the FIB angle of incidence causes rounding of the top edges of an FIB cut and the sidewalls to be inclined a few degrees from the perpendicular (the exact angles depend on the ion beam profile and milled depth). Redeposition may also cause the sidewalls to incline.As the milling depth increases, the probability of the sputtered material redepositing onto the sidewalls increases. If a line or hole is milled 10 to 15 times deeper than its width, redeposition results in V-shaped cross sections. The aspect ratio (depth to width) can be improved by using gas-enhanced etching (see the article by MoberlyChan et al. in this issue). Because the shape of a cut is dependent on the milled depth, the milling is referred to as 2D patterning if the sputtered depth is <100 nm, and 3D micromachining if the sputtered depth is >100 nm. FIB 2D PatterningFIB 2D patterning is used to pattern a diverse range of materials into dots, lines, and arrays. The 2D pattern densities MRS BULLETIN • VOLUME 32 • MAY 2007 • www/mrs.org/bulletin 417 AbstractThis article discusses applications of focused ion beam micro-and nanofabrication. Emphasis is placed on illustrating the versatility of focused ion beam and dual-platform systems and how they complement conventional processing techniques. The article is divided into four parts: maskless milling, ion beam lithography, ion implantation, and techniques such as in situ micromanipulation.

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“…Some results in the literature can be cited where similar MR curves to the two types observed here have been reported in polycrystalline systems, patterned by different techniques. Examples of structure A-type MRs have been observed for hundreds of nanometers-wide NWs [27][28][29][30] or nanobridges between two electrodes [31]. Also some examples of structure B-type MR are found in NWs with constrictions [7,32] or protrusions [33], in interconnected NWs with two different widths [30] as well as in nanocontacts between two wires [18,34].…”

Section: Magnetoresistance Measurementsmentioning

confidence: 99%

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

et al. 2012

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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.

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Magnetoresistance of nickel nanocontacts fabricated by different methods

Cited by 8 publications

References 26 publications

Ballistic magnetoresistance?

Ballistic magnetoresistance?

Focused Ion Beam Micro- and Nanoengineering

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

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