Fabrication and simulation of nanostructures for domain wall magnetoresistance studies on nickel

Claudio-Gonzalez, David; Husain, Muhammad; Groot, C. H. de; Bordignon, G.; Fischbacher, Thomas; Fangohr, Hans

doi:10.1016/j.jmmm.2009.02.142

Cited by 9 publications

(7 citation statements)

References 17 publications

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“…Domain wall magneto-resistance (DWMR) occurs when electrons travel from one side of the magnetic domain wall to another non-adiabatically. The DWMR is reported in many different structures such as ring structure [3][4][5] , line structure [6][7][8][9][10][11] , atom-contact structure 12,13 , zigzag structure 14,15 and bridge structure 16,17 . In line-shape devices, the magneto-resistance effect of the domain wall is relatively small because the classic resistance of the line hides the DWMR effect.…”

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confidence: 99%

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Magnetoresistance in a lithography defined single constrained domain wall spin-valve

Wang

Groot

Claudio-Gonzalez

et al. 2010

Applied Physics Letters

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In 1999, Bruno [1] proposed that in nano-structured devices the domain wall width can be constricted by geometric means. A sudden large expansion of the magnetic area will constrict the domain wall as the cost of increasing the area of the domain wall outweighs the exchange interaction. In this work we report the experimental realisation of this proposed structure and show magneto-resistance in a lithographically defined constrain domain wall structure in between two independently switching single magnetic domains. This is the first in-plane transport measurement of an individual magnetic structure completely at the nano-scale using lithography. Fig. 1 shows the scanning electron microscopy image of the Ni domain wall structure and the Au contact lines, both defined by e-beam lithography and lift-off. The Au structure allows a four point measurement technique to be employed in the measurement of the domain wall structure such that only the Ni structure contributes to the resistance. Fig. 2 shows the room temperature magneto-resistance effect of the nano-bridge. The resistance-field pattern shows the typical step-like behaviour of a spin-valve like MR structure in which both sides switch independently. The high coercive side (100 by 400 nm2 domain; left side in Fig. 1) switches at around 25mT and the low coercive side (200 by 400 nm2 domain) switches near 5 mT. These experimental values are slightly smaller than those derived from an OOMMF simulation. Nevertheless, a clear plateau is identified in the MR curve in which the domains are anti-parallel leading to a domain wall in the nano-bridge and hence domain wall magneto-resistance of around 0.1% or 0.4 Ohm. We have previously shown [2] using a micromagnetic simulation that the domain wall width can be reduced by scaling the geometrical size of the bridge either through a reduction of the s0=s1 ratio or through limiting the bridge length 2d0. Using the experimental ratio of s0=s1 = 0:10, we can calculate the value of the domain wall width once demagnetisation effects are taken into account. The calculated value of the domain wall width is 42 nm and using the equation for domain wall magneto-resistance by Ieda[3], this gives a resistance change of 0.4 Ohm, in agreement with the experiment. Further reduction of the length of the bridge will significantly enhance the magneto-resistance.[1] P. Bruno, Physical Review Letters 83, 2425 (1999 [2] H.

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“…The device was fabricated on a Si p-type < 100 > wafer with 17 layer was thermally grown on the front side of the wafer. Two layers of Au were deposited by photo lithography and metal lift-off.…”

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confidence: 99%

Magnetoresistance in a lithography defined single constrained domain wall spin-valve

Wang

Groot

Claudio-Gonzalez

et al. 2010

Applied Physics Letters

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“…Thus the magneto-optical effects are proportional to the spin polarization and the spin-orbit splitting of the initial and final states of the optical transition and thus are strongly affected by the matrix morphology. Furthermore, the presence of Al may quench the magnetism of the Ni atom through the existence of a nonmagnetic zone at the Ni cluster surface [15]. However, we believe that studied samples were annealed at too low temperatures to effectively create the AlNi inclusions (below 600°C).…”

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confidence: 98%

Morphology and Magneto-optical Properties of Amorphous AlN Films Doped with Nickel

et al. 2011

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Structural and magneto-optical properties of Ni-doped amorphous AlN layers (a-AlN) deposited by radio frequency (rf) sputtering on Silicon (001) substrates were investigated. The as-grown material exhibits weak ferromagnetic behavior as evidenced by the magneto-optic Kerr effect (MOKE) measurement with Kerr rotation less than 100 µrad at room temperature regardless of the Ni fraction. The samples with a Ni concentration below 10 at.% show a weak but monotonically increasing MOKE signal with post-growth annealing temperature. A hundred-fold increase in the Kerr rotation value was observed for samples with Ni content exceeding 20 at.% after thermal annealing at 450°C in nitrogen; and the Kerr rotation value abruptly decreases above that temperature. The morphology of as-grown and annealed a-AlN:Ni films were characterized by small angle x-ray scattering and transmission electron microscopy. It was found that the as-deposited film contains nano-particles of different sizes with average diameters less than 30 nm. The size distribution of nano-particles in the thermally annealed a-AlN:Ni was studied as a function of annealing time and temperature. The results correlate well with those obtained from the MOKE measurements. INTRODUCTIONMagnetically ordered amorphous materials and magnets exhibit a wide range of technologically important materials that rely on magnetic ordering and the dynamic interactions between spin excitations and electronic transport phenomena [1,2]. Amorphous III-nitride semiconductors doped with Transition Metals (TM) and rare earth ions are suitable for prospective applications in spintronics because of a strong magnetic moment associated with the metallic impurities [3,4] and the possibility of easy modification of the magnetic domain environment. The unique feature of a-AlN:TM, in general, is that a long-range magnetic ordering is possible, while the long-range order does not exist in the distribution of constituent atoms. This implies that magnetic and nonmagnetic atoms in an a-AlN:TM lose completely the periodicity of lattice in its crystalline counterpart and form a non-crystalline solid. The high doping of magnetic transition metals is extremely difficult with the commonly used doping technique such as thermal diffusion because the solubility of the magnetic impurities is too low, especially in III-V materials [5]. Furthermore, doping with TM at high concentrations is prone to morphological inhomogeneity like nano-size precipitates and atom clustering. Experimental techniques like small angle x-ray scattering (SAXS) and high resolution transmission electron microscopy (HRTEM) allow for detailed investigations of nano-size particles embedded in a solid-state solution. The magneto-optical Kerr effect spectroscopy gives a unique opportunity to study locally magnetism in contrast to the other typically used volumetric magnetometry techniques. Combining the MOKE and SAXS/HRTEM one should be able to study in greater detail the evolution of the magnetic properties and their origin in magnetic mater...

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“…Domain wall magnetoresistance (DWMR) occurs when electrons travel from one side of the magnetic domain wall to another non-adiabatically. The DWMR is reported in many different structures such as ring structure [3][4][5] , line structure [6,7] , atom-contact structure [8,9] , zigzag structure [10,11] and bridge structure [12,13] . In lineshape devices, the magneto-resistance effect of the domain wall is relatively small because the classic resistance of the * ydw08r@ecs.soton.ac.uk FIG.…”

Section: Introductionmentioning

confidence: 99%

Single domain wall magnetoresistance electron-beam fabrication and magnetoresistance measurement

et al. 2011

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We report a reproducible top down fabrication procedure for a single domain wall magnetoresistance H-shaped device. A bi-layer e-beam lift-off process is used and the e-beam exposure dose sensing technique and proximity effect correction are discussed, together with a method to reduce the alignment tolerance to below 20 nanometer. The domain wall width is constrained down to 37nm and room temperature domain wall magnetoresistance ratio of 0.3% was detected. The dependence of switching magnetic field to domain width will be discussed, as well as the maximum domain width which can retain its magnetisation aligned along the long axis at zero field which is found to be 210nm in our experiment.

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Fabrication and simulation of nanostructures for domain wall magnetoresistance studies on nickel

Cited by 9 publications

References 17 publications

Magnetoresistance in a lithography defined single constrained domain wall spin-valve

Magnetoresistance in a lithography defined single constrained domain wall spin-valve

Morphology and Magneto-optical Properties of Amorphous AlN Films Doped with Nickel

Single domain wall magnetoresistance electron-beam fabrication and magnetoresistance measurement

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