Effect of interdot magnetostatic interaction on magnetization reversal in circular dot arrays

Novosad, V.; Guslienko, K. Yu.; Shima, Hisashi; Otani, Y.; Kim, S. G.; Fukamichi, K.; Kikuchi, Nobuaki; Kitakami, Osamu; Shimada, Yutaka

doi:10.1103/physrevb.65.060402

Cited by 143 publications

(98 citation statements)

References 17 publications

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“…The stability of such structures has already been investigated and is well understood. [4][5][6][7][8] The uniformly magnetized domains in a Landau pattern are separated by 90°Néel walls and form an in-plane flux closure ͓yellow arrows in Fig. 1, panel ͑a͔͒.…”

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confidence: 99%

“…1, panel ͑a͔͒, which plays a key role in the magnetization dynamics. 2,3 For the experimental study of magnetic vortex structures magnetic force microscopy, 9 Lorentz microscopy, 9 spin-polarized scanning tunneling microscopy, 10 magnetic x-ray microscopy, 11 and magneto-optical techniques 5,6,12,13 can be deployed. Study of the details in the dynamic response of a vortex structure to externally applied magnetic field pulses and continuous excitations was only possible with the advent of time-resolved magnetic transmission x-ray microscopy 14,15,17 and photoemission electron microscopy.…”

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Direct observation of the vortex core magnetization and its dynamics

Chou

Puzic

Stoll

et al. 2007

Applied Physics Letters

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Square-shaped thin film structures with a single magnetic vortex were investigated using a scanning transmission x-ray microscope. The authors report on the direct observation of the vortex core in 500ϫ 500 nm 2 , 40 nm thick soft magnetic Ni-Fe samples. The static configuration of the vortex core was imaged as well as the gyrotropic motion of the core under excitation with an in-plane alternating magnetic field. This enabled them to directly visualize the direction of the out-of-plane magnetization in the vortex core ͑up or down͒. The reversal of the core was effected by short bursts of an alternating magnetic field. An asymmetry appears in the core's trajectory for its orientation pointing up and down, respectively. © 2007 American Institute of Physics. ͓DOI: 10.1063/1.2738186͔The magnetic properties of patterned ferromagnetic thin film structures are recently attracting considerable attention. The arrangement of magnetic moments in micro-and nanostructures and their excitations are key subjects to be investigated. Micromagnetic calculations were employed to predict the magnetic equilibrium state of such systems, and have been verified experimentally. The dynamics of the magnetization in these small elements, on the other hand, is much more challenging. Such investigations are not only interesting for modern magnetism theory but are also important for developing high density magnetic recording media where fast switching speeds are necessary.Micron-or submicron-sized magnetic patterns minimize their stray field energy by forming regions of inhomogeneous magnetization, e.g., domain walls. In thin film ferromagnetic structures, the competing contributions from the exchange energy between neighboring spins and long-range dipoledipole interactions can result in a very stable magnetic vortex configuration, 1 also called Landau structure in squares. The stability of such structures has already been investigated and is well understood. [4][5][6][7][8] The uniformly magnetized domains in a Landau pattern are separated by 90°Néel walls and form an in-plane flux closure ͓yellow arrows in Fig. 1, panel ͑a͔͒. The curling magnetization at the center of the element turns out of the plane avoiding a singularity and forming in this region the vortex core ͓red arrow in Fig. 1, panel ͑a͔͒, which plays a key role in the magnetization dynamics. 2,3 For the experimental study of magnetic vortex structures magnetic force microscopy, 9 Lorentz microscopy, 9 spin-polarized scanning tunneling microscopy, 10 magnetic x-ray microscopy, 11 and magneto-optical techniques 5,6,12,13 can be deployed. Study of the details in the dynamic response of a vortex structure to externally applied magnetic field pulses and continuous excitations was only possible with the advent of time-resolved magnetic transmission x-ray microscopy 14,15,17 and photoemission electron microscopy. 16 In the current work we report on the direct observation of a magnetic vortex core and its dynamic behavior under influence of an in-plane alternating magnetic field. Squar...

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Direct observation of the vortex core magnetization and its dynamics

Chou

Puzic

Stoll

et al. 2007

Applied Physics Letters

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“…Here E A is the energy barrier between two directions of the magnetic moment in a single domain nanoparticle -along and against to an applied magnetic field, t obs is the observation time, and t 0 is the characteristic time constant, called the attempt frequency. On the other hand, the magnetic vortex also has two different magnetic states separated by an energy barrier, owing to two key properties: chirality (clockwise or counterclockwise) and polarity (positive or negative) [20]. It is reasonable to suggest that below a certain temperature these states can be blocked (or frozen) if the thermal energy becomes smaller than the energy barrier between different states of the magnetic vortex.…”

Section: Discussionmentioning

confidence: 99%

“…Consequently, the individual crystallites in the nanoclustered film can be treated as the independent magnetic domains with the abnormally small interdomain separation. Such type of the magnetic objects lower their magnetostatic energy by forming the closure-domain [19] or the magnetic vortex [20] structure. Therefore, the nanocrystalline clusters in this film are not the FM single domains and their magnetic properties can not to be correctly described in the framework of a classical Langevin statistics, expressed by Eq.…”

Section: Discussionmentioning

confidence: 99%

Nonclassical magnetic dynamics and negative exchange bias in Nd0.5Sr0.5MnO3 films

Prokhorov

Kaminsky

Komashko

et al. 2007

Low Temperature Physics

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The amorphous, nanoclustered, and self-organizing bilayered Nd Sr MnO 0.5 0.5 3 films have been prepared by a rf-magnetron sputtering. The amorphous film turn out to be a typical paramagnet with a freely moving of the individual Mn spins, the magnetic properties of which are well described by the Curie-Weiss approximation. The nanoclustered film manifests the magnetic properties mimic to the superparamagnetic particles with a nonclassical magnetic dynamics. Taking into account the unique shape of the hysteresis loops, which have hysteretic lobes at high magnetic field but are nonhysteretic as the field crosses zero, we suggest that each particle (nanocluster) is the closure magnetic domain (or magnetic vortex) rather than the single one. At the same time, the blocked to unblocked transition was observed with increasing temperature similar to the usual superparamagnet. The self-organizing bilayered film demonstrates a negative exchange bias, which is typical for the ferromagnet/antiferromagnet hybrid system in spite of that both layers in our case have a ferromagnetic origin. The magnetic properties of the films are discussed in detail on the base of modern theoretical models.

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“…Dipolar domain wall coupling is important for separations that are approximately ഛ1 ring diameter 18 and exchange coupling will also have an influence for rings in direct contact, as demonstrated for connected chains of dots and rings. [19][20][21] In the present work, we study the interaction of tri-ring structures where three rings touch each other in a triangular layout. This system is of interest because magnetically frustrated states can arise due to their geometric arrangement.…”

Section: Introductionmentioning

confidence: 99%

Frustrated magnetic vortices in a triad of permalloy rings: Magneto-optical Kerr effect, magnetic force microscopy, and micromagnetic simulations

Rose

Buchanan

et al. 2006

Phys. Rev. B

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The field dependent magnetization of three mutually touching permalloy rings were investigated by means of the magneto-optical Kerr effect, magnetic force microscopy, and micromagnetic simulations. Each ring has a width of 0.2-1.8 m, an outer diameter of 4 m, and a thickness of 17 nm. Decreasing an applied magnetic field from saturation leads to the nucleation and annihilation of magnetic vortices, leaving at least one ring in a magnetically frustrated state. The properties of the magnetization reversal strongly depend on the ring width and on the direction of the applied field. Multiple complex reversal paths with vortexlike magnetization configurations are found.

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Effect of interdot magnetostatic interaction on magnetization reversal in circular dot arrays

Cited by 143 publications

References 17 publications

Direct observation of the vortex core magnetization and its dynamics

Direct observation of the vortex core magnetization and its dynamics

Nonclassical magnetic dynamics and negative exchange bias in Nd0.5Sr0.5MnO3 films

Frustrated magnetic vortices in a triad of permalloy rings: Magneto-optical Kerr effect, magnetic force microscopy, and micromagnetic simulations

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