Magnetic force microscopy observation of antivortex core with perpendicular magnetization in patterned thin film of permalloy

Shigeto, K.; Okuno, T.; Mibu, Ko; Shinjo, Teruya; Ono, Tomoshige

doi:10.1063/1.1483386

Cited by 104 publications

(76 citation statements)

References 8 publications

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“…The magnetic coupling is suppressed and only the spin-torque contribution locks into the gyrotropic eigenmode if the sense of rotation of the applied current coincides with the intrinsic sense of gyration of the antivortex. We report on the first experimental observation of purely spin-torque induced antivortex-core reversal.Antivortices and vortices form in ferromagnetic thinfilm structures [17][18][19] by a compromise between the shape anisotropy, which prefers the magnetization being in-plane of the film as well as aligned parallel to the edges of the structure, and between the short range exchange coupling, which favors a parallel orientation within the material. Both magnetization configurations are topological counterparts with opposite winding numbers [6].…”

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confidence: 99%

“…Antivortices and vortices form in ferromagnetic thinfilm structures [17][18][19] by a compromise between the shape anisotropy, which prefers the magnetization being in-plane of the film as well as aligned parallel to the edges of the structure, and between the short range exchange coupling, which favors a parallel orientation within the material. Both magnetization configurations are topological counterparts with opposite winding numbers [6].…”

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confidence: 99%

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Magnetic Antivortex-Core Reversal by Circular-Rotational Spin Currents

Kamionka

Martens

Chou³

et al. 2010

Phys. Rev. Lett.

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Topological singularities occur as antivortices in ferromagnetic thin-film microstructures. Antivortices behave as two-dimensional oscillators with a gyrotropic eigenmode which can be excited resonantly by spin currents and magnetic fields. We show that the two excitation types couple in an opposing sense of rotation in the case of resonant antivortex excitation with circular-rotational currents. If the sense of rotation of the current coincides with the intrinsic sense of gyration of the antivortex, the coupling to the Oersted fields is suppressed and only the spin-torque contribution locks into the gyrotropic eigenmode. We report on the experimental observation of purely spin-torque induced antivortex-core reversal. The dynamic response of an isolated antivortex is imaged by time-resolved scanning transmission x-ray microscopy on its genuine time and length scale. DOI: 10.1103/PhysRevLett.105.137204 PACS numbers: 75.60.Jk, 68.37.Yz, 72.25.Àb, 75.60.Ch Magnetization dynamics in microstructures is not only an aspect of basic research. Its investigation is also motivated by the vision of engineering new storage devices. Magnetic antivortices and vortices are capable of storing binary information [1][2][3] represented by their core polarization p ¼ AE1 and behave as two-dimensional oscillators with a gyrotropic eigenmode which can be excited resonantly by spin currents and magnetic fields [4][5][6][7]. With the perspective of possible applications in storage devices, spin-torque induced core switching is preferred because in this case single elements can be addressed, which is obviously important for storage cells of high density. Another motivator to investigate the current induced dynamics of magnetization is the patent for the magnetic race track memory [8,9], which is based on the unidirectional control of magnetic domain walls in a nanowire by spinpolarized currents [10]. Thereto, a detailed understanding of the coupling between the spin of the conduction electrons and the magnetization of ferromagnets, namely, the spin-transfer torque [11][12][13], has to be gathered. Nevertheless, experiments on spin-torque driven magnetization dynamics come along with a general difficulty: the discrimination between the spin-transfer torque and the torque from parasitic Oersted fields as driving force [4][5][6][14][15][16]. Both torques are generated simultaneously by the applied current. In this Letter we show that both excitation types couple in an opposing sense of rotation in the case of resonant antivortex excitation with circular-rotational currents. The magnetic coupling is suppressed and only the spin-torque contribution locks into the gyrotropic eigenmode if the sense of rotation of the applied current coincides with the intrinsic sense of gyration of the antivortex. We report on the first experimental observation of purely spin-torque induced antivortex-core reversal.Antivortices and vortices form in ferromagnetic thinfilm structures [17][18][19] by a compromise between the shape anisotropy, which prefers the...

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confidence: 99%

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confidence: 99%

Magnetic Antivortex-Core Reversal by Circular-Rotational Spin Currents

Kamionka

Martens

Chou³

et al. 2010

Phys. Rev. Lett.

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“…Magnetic force microscope (MFM) is a powerful tool to identify the shape of magnetic domain walls and the magnetic vortex directly. 9) MFM detects the magnetic force exerted on a magnetic probe tip when the tip is scanned over the surface of the sample, and magnetic change should be observed during the phase transition. In this paper, by using MFM, we investigated the temperature dependence of magnetic domain structures of MnAs films grown on GaAs substrates.…”

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confidence: 99%

Magnetic Domain Structure of MnAs Thin Films as a Function of Temperature

et al. 2003

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We have investigated magnetic domain structures of MnAs thin films grown on GaAs substrates by a magnetic force microscope. We observed, by an atomic force microscope, rectangular defects along GaAs [110] direction which disperse randomly on the surface of MnAs/ GaAs (001). The Curie temperature of MnAs is 45 C, and it is successfully confirmed directly by the variable temperature magnetic force microscope observation. We also investigated magnetic domain structures of MnAs/GaAs (111)B, and no apparent relation was observed between the topographic structure and the magnetic domain structure.

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“…[25][26][27] Periodic vortex and antivortex arrangements have often been found as parts of cross-tie walls. 28,29 Isolated antivortices by contrast, due to their unstable state, possibly can be formed in specially designed geometric confinements. [25][26][27]29 The antivortex also appears together with vortices in dynamic transient states during vortex-core reversals in nanodots [7][8][9][10][11] and magnetization-reversal dynamics, 30 domain-wall motions in nanostrips 31,32 or highly nonlinear chaos dynamics, 33 because the total topological charge is always conserved during such dynamic phenomena.…”

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“…28,29 Isolated antivortices by contrast, due to their unstable state, possibly can be formed in specially designed geometric confinements. [25][26][27]29 The antivortex also appears together with vortices in dynamic transient states during vortex-core reversals in nanodots [7][8][9][10][11] and magnetization-reversal dynamics, 30 domain-wall motions in nanostrips 31,32 or highly nonlinear chaos dynamics, 33 because the total topological charge is always conserved during such dynamic phenomena. 34,35 Although the dynamics of single antivortices [25][26][27] and their dynamic interactions with vortices 30,36,37 have been reported in earlier studies, the dynamics of coupled vortices and antivortices in round-shaped modulated nanostrips and their coupled gyration propagation have not been well understood in the magnonic band aspect or in terms of gyration-signal propagations through 1D alternating vortex-antivortex (V-AV ) lattices.…”

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Enhanced gyration-signal propagation speed in one-dimensional vortex-antivortex lattices and its control by perpendicular bias field

Jeong

Kim

2014

Appl. Phys. Lett.

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We report on a micromagnetic simulation study of coupled core gyrations in onedimensional (1D) alternating vortex-antivortex (V-AV) lattices formed in connected softmagnetic-disk arrays. In such V-AV lattices, we found very characteristic standing-wave gyration modes as well as ultrafast gyration-signal propagation, as originating from combined strong exchange and dipole interactions between the neighboring vortices and antivortices.Collective core oscillations in the V-AV networks are characterized as unique two-branch bands that are affected by the vortex-antivortex polarization ordering and controllable by externally applied perpendicular fields. The gyration-signal propagation speed is much faster than that for 1D disk arrays composed only of vortex states, and the propagation speed for the parallel polarization ordering is increased, remarkably, to more than 1 km/s by application of perpendicular static fields. This work provides a fundamental understanding of the coupled dynamics of topological solitons as well as an additional mechanism for ultrafast gyrationsignal propagation; moreover, it offers an efficient means of significant propagation-speed enhancement that is suitable for information carrier applications in continuous thin-film nanostrips.

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Magnetic force microscopy observation of antivortex core with perpendicular magnetization in patterned thin film of permalloy

Cited by 104 publications

References 8 publications

Magnetic Antivortex-Core Reversal by Circular-Rotational Spin Currents

Magnetic Antivortex-Core Reversal by Circular-Rotational Spin Currents

Magnetic Domain Structure of MnAs Thin Films as a Function of Temperature

Enhanced gyration-signal propagation speed in one-dimensional vortex-antivortex lattices and its control by perpendicular bias field

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