Spin-Dependent Scattering in Multilayered Magnetic Rings

Castaño, Fernando; Morecroft, D.; Jung, Won; Ross, C. A.

doi:10.1103/physrevlett.95.137201

“…As the reverse f eld increases, the propagating domain walls in the NiFe meet, forming a 360 • wall on each side of the elliptical ring, similar to the 360 • walls reported in small circular rings ('twistedonion' state) [66,98,103]; the 360 • walls have an insignif cant effect on the GMR, and since the Co layer is still in the onion state, the resistance of the ring is maximum. The intermediate resistance level corresponds to the switching of the Co layer to the vortex state and the transition to the reverse onion state results again in a minimum resistance value [99]. This interpretation of the experimental results is supported by three-dimensional micromagnetic simulations of both the magnetization and of the GMR amplitude [99,100].…”

Section: Magnetic Properties Of Spin-valve Ring Elementssupporting

confidence: 69%

Ferromagnetic Nanorings

Vaz

¹

,

Hayward

²

,

Llandro

³

et al. 2007

Self Cite

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Ferromagnetic metal rings of nanometre range widths and thicknesses exhibit fundamentally new spin states, switching behaviour and spin dynamics, which can be precisely controlled via geometry, material composition and applied f eld. Following the discovery of the 'onion state', which mediates the switching to and between vortex states, a range of fascinating phenomena has been found in these structures. In this overview of our work on ring elements, we f rst show how the geometric parameters of ring elements determine the exact equilibrium spin conf guration of the domain walls of rings in the onion state, and we show how such behaviour can be understood as the result of the competition between the exchange and magnetostatic energy terms. Electron transport provides an extremely sensitive probe of the presence, spatial location and motion of domain walls, which determine the magnetic state in individual rings, while magneto-optical measurements with high spatial resolution can be used to probe the switching behaviour of ring structures with very high sensitivity. We illustrate how the ring geometry has been used for the study of a wide variety of magnetic phenomena, including the displacement of domain walls by electric currents, magnetoresistance, the strength of the pinning potential introduced by nanometre size constrictions, the effect of thermal excitations on the equilibrium state and the stochastic nature of switching events.

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“…These structures consist of a soft (free) layer (NiFe) and a hard layer (Co) separated by a non-magnetic Cu layer, suff ciently thick to largely decouple the two magnetic layers (such that interlayer exchange coupling effects are negligible). However, due to the magnetostatic coupling between the two magnetic layers (due to the stray f eld associated with the onion state), the switching properties of the soft layer are strongly affected by the stray f eld issuing from the Co layer (while the behaviour of the Co layer remains largely unaffected) [99,100,102]. Figure 6 shows examples of the magnetoresistive behaviour of pseudo-spin-valve rings, 5 μm wide, with nominal structure Au(4 nm)/Co(7 nm)/Cu(5 nm)/NiFe(4 nm)/SiO x /Si(001), for two types of ring geometries studied, circular and elliptical.…”

Section: Magnetic Properties Of Spin-valve Ring Elementsmentioning

confidence: 99%

“…Pseudo-spinvalve ring structures displaying GMR have been fabricated and their magnetization reversal investigated using magnetoresistance measurements and micromagnetic modelling [99][100][101][102]. These structures consist of a soft (free) layer (NiFe) and a hard layer (Co) separated by a non-magnetic Cu layer, suff ciently thick to largely decouple the two magnetic layers (such that interlayer exchange coupling effects are negligible).…”

Section: Magnetic Properties Of Spin-valve Ring Elementsmentioning

confidence: 99%

Ferromagnetic nanorings

Vaz

¹

,

Hayward

²

,

Llandro

³

et al. 2007

J. Phys.: Condens. Matter

View full text Add to dashboard Cite

Ferromagnetic metal rings of nanometre range widths and thicknesses exhibit fundamentally new spin states, switching behaviour and spin dynamics, which can be precisely controlled via geometry, material composition and applied f eld. Following the discovery of the 'onion state', which mediates the switching to and between vortex states, a range of fascinating phenomena has been found in these structures. In this overview of our work on ring elements, we f rst show how the geometric parameters of ring elements determine the exact equilibrium spin conf guration of the domain walls of rings in the onion state, and we show how such behaviour can be understood as the result of the competition between the exchange and magnetostatic energy terms. Electron transport provides an extremely sensitive probe of the presence, spatial location and motion of domain walls, which determine the magnetic state in individual rings, while magneto-optical measurements with high spatial resolution can be used to probe the switching behaviour of ring structures with very high sensitivity. We illustrate how the ring geometry has been used for the study of a wide variety of magnetic phenomena, including the displacement of domain walls by electric currents, magnetoresistance, the strength of the pinning potential introduced by nanometre size constrictions, the effect of thermal excitations on the equilibrium state and the stochastic nature of switching events.

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“…Thicknesses close to the modulation amplitude provide more control over the anisotropy. Additionally, the formation of a metastable single domain resists vortex formation in nanopatterned ferromagnetic thin films, which is essential for realizing devices, such as volatile memory, magnetically frustrated patterned media, 11 highly integrated nanoscale magnetic devices, 24,25 etc. Fourier analysis of magnetostatic energy for this nanomodulated film supports the existence of magnetic diploes (E da = 0).…”

Section: Discussionmentioning

confidence: 99%