Vortex core scattering and pinning by impurities in nanomagnets

Toscano, D.; Leonel, S. A.; Dias, R. A.; Coura, P. Z.; Costa, B. V.

doi:10.1063/1.3573518

Cited by 17 publications

(18 citation statements)

References 22 publications

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“…[22]. Our results [23] indicate that the possible origins of the pinning and scattering defects in thin films can be the local reduction or increase in the exchange constant respectively, caused by a local nanoscaled structural deformation during the nanofabrication process. We believe that not all structural defects produced in the samples are pinning defects, structural scattering defects can also be produced and certainly will affect the gyrotropic frequency as pointed out in Ref.…”

Section: Introductionmentioning

confidence: 72%

“…The authors argued that the fluctuations were due to a distribution of nanoscale defects pinning the vortex core. In a recent work [23] we showed the dynamical behavior of a magnetic nano-disk contaminated by pointlike impurities, using micromagnetic approach [24]. In this approach the nano-disk is partitioned into cubical working cells containing many atoms.…”

Section: Introductionmentioning

confidence: 99%

“…As in Ref. [23], using a pseudospin language, we can write a model Hamiltonian for the nano-disk with magnetic impurities and under the action of an external magnetic field as…”

Section: Introductionmentioning

confidence: 99%

“…[23] and spin dynamics simulations to study the influence of magnetic impurities in the frequency of the gyrotropic mode in nano-disks of Permalloy.…”

Section: Introductionmentioning

confidence: 99%

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The influence of magnetic impurities in the vortex core dynamics in magnetic nano-disks

Silva

Toscano

Sato

et al. 2012

Journal of Magnetism and Magnetic Materials

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a b s t r a c tIn this work we have used spin dynamics simulations to study the gyrotropic frequency behavior in nano-disks of Permalloy with magnetic impurities. We consider the effect of attractive impurity and repulsive impurity placed near the vortex core gyrotropic trajectory. We observed that the gyrotropic frequency is affected by the presence of impurity. The gyrotropic frequency shift depends on the relative position between the impurity and the vortex core gyrotropic trajectory and if impurity is attractive or repulsive. Our results agree with the analytical model and with experimental behavior for the gyrotropic frequency shown in the literature.& 2012 Elsevier B.V. All rights reserved.The magnetic devices can be used in many technological applications, for example in magnetic random access memories (MRAMs), digital reading heads, position sensors, devices for measurements of currents to applications in medicine in cancer treatment for example [1][2][3][4][5][6]. It was discovered recently that some magnetic nano-structures can present interesting properties that may lead to build efficient new storage devices [7-10]. Magnetic nano-device like a nano-disk shows a magnetic vortex configuration in ground state. The competition between magnetostatic energy and the exchange interaction is responsible for the formation of this magnetic vortex configuration in nano-disks [11]. The study of the dynamics of the vortex and a way to control the core magnetization is of paramount importance since the Z 2 symmetry of the vortex core [12,13] can be used as a bit in store devices. In numerical simulations it was observed that switching can be induced by vortex-hole interaction [14] or by the application of a time dependent external magnetic field which induces a vortex gyrotropic motion [15,16].In the last few years the interaction of the vortex core with defects and impurities in magnetic materials has been the subject of intense investigation [17][18][19]. Even in pure samples, such as nano-disks made of Permalloy, structural defects are distributed randomly through the material. As example, the density of defects can be up to % 2 Â 10 11 =cm 2 for the pinning sites in Permaloy nanodisks that affect the vortex dynamics [20]. The pinning behavior of magnetic vortices was investigated by using Lorentz transmission electron microscopy [21]. Recently, the vortex core dynamics in individual magnetic disks was investigated using time-resolved Kerr microscopy [22]; it was observed fluctuations in the frequency of the gyrotropic mode in nano-disks of Permalloy. The authors argued that the fluctuations were due to a distribution of nanoscale defects pinning the vortex core. In a recent work [23] we showed the dynamical behavior of a magnetic nano-disk contaminated by pointlike impurities, using micromagnetic approach [24]. In this approach the nano-disk is partitioned into cubical working cells containing many atoms. Each working cell has dimensions a Â a Â a and volume v cell ¼ a 3 , where a is greater than unit cell para...

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Section: Introductionmentioning

confidence: 72%

Section: Introductionmentioning

confidence: 99%

“…As in Ref. [23], using a pseudospin language, we can write a model Hamiltonian for the nano-disk with magnetic impurities and under the action of an external magnetic field as…”

Section: Introductionmentioning

confidence: 99%

“…[23] and spin dynamics simulations to study the influence of magnetic impurities in the frequency of the gyrotropic mode in nano-disks of Permalloy.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

The influence of magnetic impurities in the vortex core dynamics in magnetic nano-disks

Silva

Toscano

Sato

et al. 2012

Journal of Magnetism and Magnetic Materials

Self Cite

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“…Theoretical works have shown that the energy and stability of these topological excitations depend on the curvature of the ferromagnetic nanoparticle [10] and their dynamical properties are affected by both: the interaction with curve defects appearing during the fabrication of the nanomagnets [11]; and the presence of magnetic/non-magnetic impurities in these magnetic nanoparticles [12].…”

Section: Introductionmentioning

confidence: 99%

Topological Spin Excitations Induced by an External Magnetic Field Coupled to a Surface with Rotational Symmetry

Carvalho-Santos

Dandoloff

2013

Braz J Phys

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We study the Heisenberg model in an external magnetic field on curved surfaces with rotational symmetry. The Euler-Lagrange static equations, derived from the Hamiltonian lead to the inhomogeneous double sine-Gordon equation (DSG). However, if the magnetic field is coupled with the metric elements of the surface, and consequently, its curvature, the homogeneous DSG appears and a 2π-soliton is obtained as a solution for this model. In order to obey the self-dual equations, surface deformations are predicted at the sector where the spins point in the opposite direction to the magnetic field. The model was used to particularize the characteristic lenght of the 2π-soliton for three specific rotationally symmetric surfaces: the cylinder, the catenoid and the hyperboloid. Fractional 2π-solitons must appear on finite surfaces, as the sphere, torus and barrels, for example.

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