Magnetization switching of submicrometer Co dots induced by a magnetic force microscope tip

Kleiber, M.; Kümmerlen, F.; Löhndorf, M.; Wadas, A.; Weiss, Dieter; Wiesendanger, R.

doi:10.1103/physrevb.58.5563

Cited by 82 publications

(44 citation statements)

References 15 publications

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“…Previous studies on MFM were focused mainly on magnetic recording media (5) and multidomain magnetic materials (6,7) as well as on tip characterization (8) and image interpretation (9,10). Closer to our work, there were reported the imaging and remagnetization of Co magnetic dots (with lateral dimensions of 140 × 250 nm) (11) and imaging and magnetic moment estimation of magnetotactic bacteria (50 nm in length and 17.5 nm in radius, if modeled as a cylinder) (12). In this work we investigate both theoretically and experimentally the possibility of magnetic imaging of magnetite nanoparticles (10 nm in diameter on the average), previously dispersed in cyclohexane and grafted with oleic acid, the dispersion being known as a ferrofluid or magnetic fluid (13).…”

Section: Introductionmentioning

confidence: 82%

Atomic Force Microscopy and Magnetic Force Microscopy Study of Model Colloids

Raşa

Kuipers

Philipse

2002

Journal of Colloid and Interface Science

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Atomic force microscopy (AFM) is used to study the size, shape, and polydispersity of a variety of magnetic and nonmagnetic model colloids, previously imaged by transmission electron microscopy (TEM) only. Both height and phase images are analyzed and special attention is given to 3D morphology and softness of particles, as well as structures and presence of secondary components in the colloid, difficult to investigate with TEM. Several methods of tip characterization followed by deconvolution were applied in order to improve the accuracy of lateral diameter determination. In the case of magnetite particles dispersed in conventional ferrofluids, we explore both experimentally and theoretically the possibility of using magnetic force microscopy (MFM). We propose and discuss several models which allow to estimate the magnetic moment of a single domain superparamagnetic sphere using MFM, which cannot be done with other techniques; alternatively the tip magnetization can be determined. C 2002 Elsevier Science (USA)

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Section: Introductionmentioning

confidence: 82%

Atomic Force Microscopy and Magnetic Force Microscopy Study of Model Colloids

Raşa

Kuipers

Philipse

2002

Journal of Colloid and Interface Science

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“…The magnetic islands can be polarized via magnetic field and locally switched using a coercive field and conventional magnetic-force microscopy techniques (see e.g. [24]). The quantum well will be locally exposed to the fringe fields of the ferromagnetic islands.…”

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confidence: 99%

Fractional charge and quantized current in the quantum spin Hall state

2008

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A profound manifestation of topologically non-trivial states of matter is the occurrence of fractionally charged elementary excitations. The quantum spin Hall insulator state is a fundamentally novel quantum state of matter that exists at zero external magnetic field. In this work, we show that a magnetic domain wall at the edge of the quantum spin Hall insulator carries one half of the unit of electron charge, and we propose an experiment to directly measure this fractional charge on an individual basis. We also show that as an additional consequence, a rotating magnetic field can induce a quantized dc electric current, and vice versa. 1Soon after the theoretical proposal of the intrinsic spin Hall effect [1,2] in doped semiconductors, the concept of a time-reversal invariant spin Hall insulator [3] was introduced. In the extreme quantum limit, a quantum spin Hall (QSH) insulator state has been proposed for various systems [4,5,6]. The QSH insulators are time-reversal invariant and have a bulk charge-excitation gap. However, this system also possesses topologically protected gapless edge states that lie inside the bulk insulating gap. The edge states of the QSH insulator state differ from the quantum Hall effect and have a distinct helical property: two states with opposite spin-polarization counter-propagate at a given edge [4,7,8]. The edge states come in Kramers' doublets, and time reversal symmetry ensures the crossing of their energy levels at special points in the Brillouin zone. Because of this level crossing, the spectrum of a QSH insulator cannot be adiabatically deformed into a topologically trivial insulating state; therefore, in this precise sense, the QSH insulators represent a topologically distinct new state of matter.Recently, the QSH effect has been theoretically proposed [6] and experimentally observed [9] in HgTe quantum wells. In this experiment, an applied gate voltage can tune the carrier type from n-type doping to p-type doping, passing through a nominally insulating state. A residual charge conductance approaching 2e 2 /h has been measured in this insulating regime. Furthermore, the residual charge conductance is independent of the width of the sample, indicating that it is due to the helical edge state channels of the QSH insulator. liquid at a given edge of the QSH insulator has only two: a spin up (or down) right mover and a spin down (or up) left mover. Therefore, the helical liquid has half the degrees of freedom of a conventional one-dimensional system, and thus avoids the doubling problem.Because of this fundamental topological property of the helical liquid, a domain wall carries charge e/2. We propose a Coulomb blockade experiment to observe this fractional charge.As a temporal analog of the fractional charge effect, the pumping of a quantized charge current during each periodic rotation of a magnetic field is also proposed. This provides a direct realization of Thouless's topological pumping [14].Theoretical description. In the absence of time-reversal symmetry (TRS) br...

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“…The fabrication, magnetic characterization, 4,5 and manipulation of these types of magnets with local magnetic probes [6][7][8] have been demonstrated, and research is currently being conducted to better understand their physical properties and improve the crystalline anisotropy. The second proposed design for patterned single magnetic domain per bit storage is the perpendicular version, where the particle long axis is oriented perpendicular to the medium surface.…”

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confidence: 99%

Writing and reading of single magnetic domain per bit perpendicular patterned media

Todorovic

Schultz

Wong

et al. 1999

Applied Physics Letters

125

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By fabricating patterned media with a large number of nanoscale single domain magnetic particles embedded in a nonmagnetic substrate, and by writing the magnetization for each of these particles in a desired direction, nonvolatile magnetic storage of information could reach densities much higher than what is currently thought possible for longitudinal continuous media. We have fabricated high aspect ratio perpendicular nickel columnar nanoparticles embedded in a hard Al 2 O 3 /GaAs substrate. We show that the magnetization states of the individual magnets can be controlled by demonstrating that prototype patterned ''single magnetic domain per bit'' data tracks can be written and read back using current magnetic information storage technology.

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Magnetization switching of submicrometer Co dots induced by a magnetic force microscope tip

Cited by 82 publications

References 15 publications

Atomic Force Microscopy and Magnetic Force Microscopy Study of Model Colloids

Atomic Force Microscopy and Magnetic Force Microscopy Study of Model Colloids

Fractional charge and quantized current in the quantum spin Hall state

Writing and reading of single magnetic domain per bit perpendicular patterned media

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