Magnetic Ground State of Single and Coupled Permalloy Rectangles

Hankemeier, S.; Frömter, Robert; Mikuszeit, N.; Stickler, Daniel; Stillrich, Holger; Pütter, Sabine; Vedmedenko, E. Y.; Oepen, Hans Peter

doi:10.1103/physrevlett.103.147204

Cited by 30 publications

(21 citation statements)

References 19 publications

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“…The cross-tie state is well described in the literature. 23 The vortex diamond state coincides with the described antivortex one up to interchanging of positions of vortices and antivortices, this state was already observed in rectangular [24][25][26] and elliptical 27 nanopaticles and also in mesoscopic islands of complicated form. 24 The quasicrystal state is very similar to the vortex-antivortex lattice recently predicted for wide films 10,11 .…”

supporting

confidence: 60%

Periodic magnetic structures generated by spin–polarized currents in nanostripes

Volkov¹,

Kravchuk²,

Sheka³

et al. 2013

Appl. Phys. Lett.

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The influence of a spin-polarized current on long ferromagnetic nanostripes is studied numerically. The current flows perpendicularly to the stripe. The study is based on the Landau-Lifshitz phenomenological equation with the Slonczewski-Berger spin-torque term. The magnetization behavior is analyzed for all range of the applied currents, up to the saturation. It is shown that the saturation current is a nonmonotonic function of the stripe width. For a stripe width increasing it approaches the saturation value for an infinite film. A number of stable periodic magnetization structures are observed below the saturation. Type of the periodical structure depends on the stripe width. Besides the one-dimensional domain structure, typical for narrow wires, and the two-dimensional vortex-antivortex lattice, typical for wide films, a number of intermediate structures are observed, e.g. cross-tie and diamond state. For narrow stripes an analytical analysis is provided.PACS numbers: 75.10. Hk, 75.40.Mg, 72.25.Ba, A magnetic nanostripe is a convenient system for studying the dynamics of magnetization structures driven by a spin-polarized current. Typically the current is passed along the stripe, which causes a movement of the domain wall. This phenomenon is widely studied both theoretically and experimentally, see e.g. reviews 1-4. Nevertheless the influence of a perpendicular current on the stripe magnetization dynamics is also of high interest for spintronic applications. Recently it was predicted theoretically 5 and later confirmed experimentally 6-9 that the perpendicular current can excite the domain wall motion with much higher velocity comparing to the in-plane current.Recently we have studied the action of the strong perpendicular spin-polarized current on a nanomagnet for two limit cases, namely a planar two-dimensional film 10,11 and a narrow one-dimensional wire 12 . In both cases a stable periodical structure induced by the spincurrent is found in the pre-saturated regime: a square vortex-antivortex lattice is formed in a film and a onedimensional domain structure is formed in a wire. The aim of this paper is to make a link between these limit cases. For this purpose we consider thin and long stripe shaped samples of different widths. By varying the stripe width we study the current induced magnetization behavior in wide range, starting from quasi-one dimensional narrow strips (w/h 1) and up to quasi two-dimensional wide strips (w/h 1), where w and h denote respectively the stripe width and thickness. The following analysis is made under the assumption that the stripe is sufficiently long, so that L w and L h with L being the stripe length. We also assume that the stripe is thin enough to ensure uniformity of the magnetization along the thickness. Details of the problem geometry are shown in Fig. 1.Our study is based on the Landau-Lifshitz-Slonczewski phenomenological equation [13][14][15] : where m = M /M s = (m x , m y , m z ) is the normalized magnetization, M s is the saturation magnetization. The overdot in...

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supporting

confidence: 60%

Periodic magnetic structures generated by spin–polarized currents in nanostripes

Volkov¹,

Kravchuk²,

Sheka³

et al. 2013

Appl. Phys. Lett.

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“…The second reason is that the Landau state creates stray fields that are caused by a slight tilting of the magnetization in the large domains out of the direction parallel to the long axis. 29,31 External fields along the short axis can easily affect that pre-existing tilting and increase the angle of tilt even at small fields. Hence, a magnetization tilting in the Landau structure occurs.…”

Section: B Hard-axis Magnetization Behaviormentioning

confidence: 99%

Magnetic energies of single submicron permalloy rectangles determined via magnetotransport

et al. 2009

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We have investigated the magnetic properties of single submicron permalloy rectangles with a thickness of 20 nm and an aspect ratio of 2:1 via anisotropic magnetoresistance ͑AMR͒. Preparation and investigation via magnetotransport are performed in situ in ultrahigh vacuum. The field-dependent magnetization behavior of the two generic cases with the magnetic field applied perpendicular and parallel to the long axis of the rectangles is studied. Due to the high sensitivity of our setup, single field sweeps are sufficient to obtain magnetoresistance curves of structures with dimensions as small as 600ϫ 300 nm 2 . To link features of the AMR to changes in the micromagnetic states, the remanent state has been investigated via scanning electron microscopy with polarization analysis. Our main result is that the energy density of micromagnetic states can be obtained from the hard-axis magnetization behavior. It is demonstrated that a C/S state can be distinguished from a Landau state and the energy difference between both states is determined.

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“…3 In microstructures it has been found that the sense of rotation of the vortex is affected by magnetic structures in the vicinity. [4][5][6][7] The ability to switch or set the sense of rotation and the polarity, i.e., the magnetization orientation of the vortex core, is a field of intense research. Recent publications demonstrate the possibility to change the sense of rotation in asymmetric single nanorings [8][9][10] and nanodisks 11 by applying external fields.…”

Section: Introductionmentioning

confidence: 99%

Controlling the properties of vortex domain walls via magnetic seeding fields

et al. 2010

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The seeding of vortex domain walls in soft magnetic V-shaped nanowires by magnetic fields has been investigated via scanning electron microscopy with polarization analysis and micromagnetic simulations. It is found that the orientation of the magnetic seeding field determines the sense of rotation and the position of single vortex domain walls in the state of remanence. The topology of the magnetic microstructure in combination with symmetry considerations gives the key for the explanation of this behavior.

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Magnetic Ground State of Single and Coupled Permalloy Rectangles

Cited by 30 publications

References 19 publications

Periodic magnetic structures generated by spin–polarized currents in nanostripes

Periodic magnetic structures generated by spin–polarized currents in nanostripes

Magnetic energies of single submicron permalloy rectangles determined via magnetotransport

Controlling the properties of vortex domain walls via magnetic seeding fields

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