GMR sensor scheme with artificial antiferromagnetic subsystem

Berg, Holger; Clemens, W.; Gieres, G.; Rupp, G.; Schelter, W.; Vieth, M.

doi:10.1109/20.539099

Cited by 137 publications

(44 citation statements)

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“…Fe/Si/Fe structures are attracting interest due to strong antiferromagnetic ͑AF͒ coupling which is of significance in applications using artificial antiferromagnets and ferrimagnets as, for instance, in magnetic sensors 1 or more recently in antiferromagnetically coupled ͑AFC͒ storage media for hard disk drives. 2 Fe/Si/Fe structures are complex objects for the study of magnetic and transport properties because of the interdiffusion at interfaces with the possible formation of iron silicides of different structure and composition.…”

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confidence: 99%

Enhanced antiferromagnetic exchange coupling in Fe/Si/Fe epitaxial trilayers with Fe0.5Si0.5 boundary layers

Gareev

Bürgler

Büchmeier

et al. 2002

Applied Physics Letters

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Epitaxial Fe/Fe 0.5 Si 0.5 /Si-wedge/Fe 0.5 Si 0.5 /Fe structures are prepared by thermal evaporation with Fe 0.5 Si 0.5 boundary layers grown by coevaporation at 200°C. Magnetic properties are examined with Brillouin light scattering and longitudinal magneto-optic Kerr effect hysteresis. The interlayer coupling is found to increase in excess of 8 mJ/m 2 by introducing a boundary layer at the bottom interface. The coupling maximum shifts from 7 to 3 Å nominal Si thickness. This effect is related to reduced interdiffusion with the formation of an epitaxial, pinhole-free spacer at smaller thickness. Together with the strong increase of the coupling for decreasing spacer thickness, this results in an enhancement of the coupling. © 2002 American Institute of Physics. ͓DOI: 10.1063/1.1499229͔ Fe/Si/Fe structures are attracting interest due to strong antiferromagnetic ͑AF͒ coupling which is of significance in applications using artificial antiferromagnets and ferrimagnets as, for instance, in magnetic sensors 1 or more recently in antiferromagnetically coupled ͑AFC͒ storage media for hard disk drives. 2 Fe/Si/Fe structures are complex objects for the study of magnetic and transport properties because of the interdiffusion at interfaces with the possible formation of iron silicides of different structure and composition. [3][4][5][6][7] As was shown earlier, Si grown on Fe tends to interdiffuse and to crystallize in epitaxially stabilized CsCl-type, metallic Fe 0.5 Si 0.5 ͑Ref. 3͒ and exhibits an exponential decay of coupling versus spacer thickness ͑Refs. 5 and 7͒. This unusual behavior was related to a new type of exchange coupling across metallic-type spacers 5 in contradiction with the standard quantum interference model ͑QIM͒ of interlayer coupling. 8 The QIM predicts an exponential decay of AF coupling only for nonconducting spacers but oscillatory coupling for metallic spacers.In order to distinguish metallic and insulating-type spacers, we have previously prepared epitaxial Fe/Fe 1Ϫx Si x /Fe trilayers by codeposition of Fe and Si instead of relying on interdiffusion. We achieved a spacer composition close to Fe 0.5 Si 0.5 ͑Ref. 9͒ and spacers with variable Si content x in the range 0.4ϽxϽ1 ͑Ref. 10͒. We deposited Fe 0.5 Si 0.5 spacer layers at an elevated temperature (200°C) in order to form metallic, epitaxial iron silicides and obtained weak oscillatory coupling ͑less than 1 mJ/m 2 ͒. 9 In these samples, the coupling strength increased with decreasing temperature in agreement with the QIM for metallic spacers. 8 Second, we showed that the interlayer exchange coupling strongly increases with the nominal Si content x in epitaxial Fe 1Ϫx Si x spacers exceeding 5 mJ/m 2 for nominally pure Si spacers. With the increase of nominal Si content x, the thickness of the strongest AF coupling (t max ) shifted to a smaller Si thickness. We concluded that the very strong coupling ͑more than 5 mJ/m 2 ͒ observed for nominally pure Si spacers is not due to metallic iron silicides, but due to highly resistive, Si-rich spacers...

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confidence: 99%

Enhanced antiferromagnetic exchange coupling in Fe/Si/Fe epitaxial trilayers with Fe0.5Si0.5 boundary layers

Gareev

Bürgler

Büchmeier

et al. 2002

Applied Physics Letters

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“…Synthetic spin valves, which were first suggested by Berg et al [52] The GMR bilayer structure stack at the bottom shows strong interlayer exchange coupling and defines the magnetisation direction of the pinned ferromagnetic layer. The free layer is decoupled from the pinned layer by the relatively thick spacer in the sandwich, enabling a spin valve response.…”

Section: Fig 313 Normalised Pinning Field Versus Temperature For Spmentioning

confidence: 99%

In situ magnetoresistance measurements during patterning of spin valve devices

Morecroft

Prieto

Leung

et al. 2002

Journal of Applied Physics

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This dissertation describes an experimental study on the patterning of thin films and spin valve devices. Initially the change in the magnetisation reversal of ferromagnetic Ni 80 Fe 15 Mo 5 thin films was investigated as the shape anisotropy was increased using optical lithography to pattern wire arrays. These structures show a progressive increase in coercivity and a transition between single and two-stage reversal with increasing milling depth. A similar patterning technique was applied to unpinned (Ni 80 Fe 20 /Cu/Ni 80 Fe 20 ) pseudo spin valve (PSV) structures in order to enhance the coercivity of one of the ferromagnetic layers.The increased coercivity induced by micropatterning changed the natural similarity of the magnetic layers and the structure exhibited a small spin valve response. These initial measurements were carried out with separate milling and electrical characterisation steps.However, it was decided that it would be ideal to design a technique to do in-situ magnetoresistance measurements during milling. This meant that the samples could be milled and characterised in the same step, leading to a much cleaner and more efficient process. In-situ magnetoresistance measurements were carried out during micropatterning of PSV devices, and the measurements showed the evolution in the electrical response as wire structures were gradually milled through the thickness. Contrary to what was expected, the structures showed a maximum spin valve response when fully milled through. The effect of further increasing the shape anisotropy by reducing the wire width, and changing the material properties in the PSV structure has also been investigated. MR measurements were taken as the temperature was increased from 291K to 493K, and the results show that the patterned PSV structures have a better thermal stability than exchange biased spin valves with an IrMn pinning layer.The experiment was extended to the nanoscale, and the results show that a significant increase in MR is not observed despite the fact that the magnetic configuration tends more towards single domain. This is thought to be due to an increase in the initial resistance of the structures. A small increase in MR was observed as the wire width was decreased from 730 to 470nm, although the spin valve response is heavily dependent on the gallium dosage density during patterning in the Focused Ion Beam (FIB). Micromagnetic simulations were carried out, which agree with the experimental results and showed the change in the magnetisation reversal from rotation to switching as the dimensions were reduced on the nanoscale.ii Preface This dissertation is submitted for the degree of Doctor of Philosophy in the University of Cambridge. Except where specific reference is made, this is entirely my own work and includes nothing that is the outcome of work done in collaboration. No part of this thesis has been or is being submitted for any other qualification at this or any other university. This dissertation does not exceed the limit of length.Some of th...

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“…The digital 1 and 0 memory states are set by the relative parallel or antiparallel alignment of the two magnetic layers. The magnetization direction of the bottom layer is pinned in one direction by a synthetic antiferromagnet [23,24] whilst the magnetization of the top layer is free to rotate under the influence of an applied magnetic field or spin-polarized current.…”

Section: Introductionmentioning

confidence: 99%

Multilevel 3 Bit-per-cell Magnetic Random Access Memory Concepts and Their Associated Control Circuit Architectures

Cramman

Eastwood

King

et al. 2012

IEEE Trans. Nanotechnology

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GMR sensor scheme with artificial antiferromagnetic subsystem

Cited by 137 publications

References 3 publications

Enhanced antiferromagnetic exchange coupling in Fe/Si/Fe epitaxial trilayers with Fe0.5Si0.5 boundary layers

Enhanced antiferromagnetic exchange coupling in Fe/Si/Fe epitaxial trilayers with Fe0.5Si0.5 boundary layers

In situ magnetoresistance measurements during patterning of spin valve devices

Multilevel 3 Bit-per-cell Magnetic Random Access Memory Concepts and Their Associated Control Circuit Architectures

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