Konstantin Guslienko | University of the Basque Country, Euskal Herriko Unibertsitatea (original) (raw)

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Papers by Konstantin Guslienko

Research paper thumbnail of IG-04 - Skyrmions in 3D soft magnetic nanodots with no Dzyaloshinskii-Moriya interactions

Abstract: Skyrmions typically appear in systems with perpendicular magnetic anisotropy (PMA) and ... more Abstract: Skyrmions typically appear in systems with perpendicular magnetic anisotropy (PMA) and Dzyaloshinskii-Moriya interactions (DMI). Bloch skyrmion states can be stabilized in magnetic dots with no need of DMI [1]. However, PMA is typically considered to be necessary. Nanoparticle geometry is an additional important factor for the skyrmion stabilization due to the influence of magnetostatic energy. Therefore, the sample shape (e.g. spherical) can result in stabilization of the skyrmions [2]. Recently, stabilization of the half-hedgehog skyrmions in soft magnetic (Permalloy) hemispherical dots by the MFM tip was demonstrated [3].<br/>Here we conduct micromagnetic simulations in 3D soft magnetic dots with planar (cylindrical) or curved (spherical cap) geometry with neither PMA nor DMI. The geometries of both magnetic elements correspond to the base radius 60-120 nm and the aspect ratio thickness/ radius ranged from 0.4 to 2 and magnetic parameters of permalloy. In a wide r...

Research paper thumbnail of Inertial Domain Wall Motion Driven by Staggered Spin-Orbit Fields in Uncompensated Antiferromagnets

Research paper thumbnail of Broadband communication and information processing with edge spin waves

Bulletin of the American Physical Society, 2019

El gobierno corporativo de las sociedades mercantiles y la protección de los accionistas minorita... more El gobierno corporativo de las sociedades mercantiles y la protección de los accionistas minoritarios José Mª López Jiménez Resumen: En este artículo se muestra la importancia de las disposiciones de gobierno corporativo en la gestión, especialmente, de las grandes sociedades de capital, y se identifican algunas medidas promovidas normativamente para fomentar la participación activa de los pequeños inversores, entre otros accionistas, en la vida de estas sociedades.

Research paper thumbnail of Half-hedgehog spin textures in sub-100 nm soft magnetic nanodots

Nanoscale, 2020

Permalloy hemispherical nanodots are able to host three-dimensional chiral structures (half-hedge... more Permalloy hemispherical nanodots are able to host three-dimensional chiral structures (half-hedgehog spin textures) with non-zero topological charge at room temperature and in absence of DMI interaction.

Research paper thumbnail of Effective dipolar boundary conditions for dynamic magnetization in thin magnetic stripes

Physical Review B, 2002

We show that dynamic magnetization at the lateral edges of a thin, axially magnetized magnetic el... more We show that dynamic magnetization at the lateral edges of a thin, axially magnetized magnetic element with finite in-plane size can be described by effective ''pinning'' boundary conditions. This effective pinning is of a purely dipolar nature, is not related to the magnetocrystalline surface anisotropy of the magnetic material, and is determined by the inhomogeneity of the dynamic demagnetizing field near the edges of the element. Eigenfunctions and eigenvalues obtained using these effective boundary conditions give quantitative description of the quantized spin wave spectra experimentally observed in long and thin permalloy stripes of a micron-size width.

Research paper thumbnail of Evolution and stability of a magnetic vortex in a small cylindrical ferromagnetic particle under applied field

Research paper thumbnail of Probing the Anharmonicity of the Potential Well for a Magnetic Vortex Core in a Nanodot

Physical Review Letters, 2013

Research paper thumbnail of Probing dynamical magnetization pinning in circular dots as a function of the external magnetic field orientation

Physical Review B, 2012

ABSTRACT We performed ferromagnetic resonance measurements of square arrays of noninteracting Per... more ABSTRACT We performed ferromagnetic resonance measurements of square arrays of noninteracting Permalloy circular dots for different orientations of external magnetic field with respect to the patterned film plane (θ). Out-of-plane angular dependence of the main resonance peak was measured in the whole range of the field angles 0° ⩽ θ ⩽ 90°. The main eigenmodespatial distribution is strongly nonuniform due to the dot nonellipsoidal shape. Nevertheless, for dots with small aspect ratio b=L/R⩽0.1 (where R is dot radius and L is dot thickness) Kittel&amp;#39;s equation, assuming uniform dynamic magnetization (no pinning at the dot lateral edges), describes the peak position with high accuracy. Analytical calculations and micromagnetic simulations confirmed the gradual evolution of the main mode profile and a smooth transition from the strong to relatively weak pinning conditions with the change of external magnetic field angle.

Research paper thumbnail of Quasiuniform magnetization state in soft ferromagnetic nanocylinders

Research paper thumbnail of Localized domain-wall excitations in patterned magnetic dots probed by broadband ferromagnetic resonance

Physical Review B, 2011

We investigate the magnetization dynamics in circular Permalloy dots with spatially separated mag... more We investigate the magnetization dynamics in circular Permalloy dots with spatially separated magnetic vortices interconnected by domain walls (double vortex state). We identify a novel type of quasi one-dimensional (1D) localised spin wave modes confined along domain walls, connecting each of two vortex cores with two edge half-antivortices. Variation of the mode eigenfrequencies with the dot size is in quantitative agreement with the developed model, which considers a dipolar origin of the localized 1D spin waves or so-called Winter´s magnons [J.M. Winter, Phys.Rev. 124, 452 (1961)]. These spin waves are analogous to the displacement waves of strings, and could be excited in a wide class of patterned magnetic nanostructures possessing domain walls, namely in triangular, square, circular or elliptic magnetic dots.

Research paper thumbnail of Stability of magnetic vortex in soft magnetic nano-sized circular cylinder

Journal of Magnetism and Magnetic Materials, 2002

Stability of magnetic vortex with respect to displacement of its center in a nano-scale circular ... more Stability of magnetic vortex with respect to displacement of its center in a nano-scale circular cylinder made of soft ferromagnetic material is studied theoretically. The mode of vortex displacement producing no magnetic charges on the cylinder side is proposed and the corresponding absolute single-domain radius of the cylinder is calculated as a function of its thickness and the exchange length of the material. In cylinders with the radii less than the single-domain radius the vortex state is unstable and is absolutely prohibited (except if pinned by material imperfections), so that the distribution of the magnetization vector in such cylinders in no applied magnetic field is uniform (or quasi-uniform). The phase diagram of nano-scale cylinders including the stability line and the metastability region obtained here is presented.

Research paper thumbnail of Multiscale versus micromagnetic calculations of the switching field reduction in FePt∕FeRh bilayers with perpendicular exchange spring

Journal of Applied Physics, 2005

Calculations of magnetisation reversal via a perpendicular exchange spring in soft-hard bilayers ... more Calculations of magnetisation reversal via a perpendicular exchange spring in soft-hard bilayers are presented using the example of an FePt/ FeRh bilayer which has recently been proposed as an alternative medium for heat-assisted magnetic recording applications. We show that the standard three-dimensional micromagnetic model fails to describe the coercivity reduction due to the fact that at low interface exchange value, the domain wall penetration into the hard layer is not correctly described within the continuous approach. A multiscale model based on atomic level simulations near the interface and a micromagnetic approach far from it is proposed. This leads to improved calculations of the exchange spring at the interface, allowing a detailed study of the magnetisation reversal dynamics. As a result, the coercivity is found to saturate at an interfacial exchange value of 4% of the bulk value, the practical applications of which are discussed. In addition, the granular structure in an FePt medium with different intergrain exchange parameters is considered.

Research paper thumbnail of Spin-waves in cylindrical magnetic dot arrays with in-plane magnetization

Journal of Applied Physics, 2000

The discrete spectrum of dipole-exchange spin-wave modes of a tangentially magnetized cylindrical... more The discrete spectrum of dipole-exchange spin-wave modes of a tangentially magnetized cylindrical magnetic dot is calculated from the solution of the Landau-Lifshitz equation and the magnetostatic Maxwell equations in a cylindrical geometry. The general surface spin-pinning conditions at the radial dot boundary are considered. The main simplifying assumptions are: ͑i͒ the dot radius is much larger than the dot height; ͑ii͒ the distribution of the variable magnetization along the dot height is uniform. The approximate dispersion equation for spin-wave modes in a dot is obtained in a simple analytical form similar to the form of the dispersion equation in an infinite film. The quantization effect of the spin-wave frequencies appears due to the finite dot radius and is essential for submicron magnetic dots. The discrete spin-wave frequencies are calculated in a practically important case of the square array of permalloy cylindrical dots. The relative intensities of spin-wave modes, when observed by Brillouin light scattering, are considered. The role of interdot dipole-dipole coupling is discussed.

Research paper thumbnail of Spin-waves in cylindrical magnetic dot arrays with in-plane magnetization

Journal of Applied Physics, 2000

The discrete spectrum of dipole-exchange spin-wave modes of a tangentially magnetized cylindrical... more The discrete spectrum of dipole-exchange spin-wave modes of a tangentially magnetized cylindrical magnetic dot is calculated from the solution of the Landau-Lifshitz equation and the magnetostatic Maxwell equations in a cylindrical geometry. The general surface spin-pinning conditions at the radial dot boundary are considered. The main simplifying assumptions are: ͑i͒ the dot radius is much larger than the dot height; ͑ii͒ the distribution of the variable magnetization along the dot height is uniform. The approximate dispersion equation for spin-wave modes in a dot is obtained in a simple analytical form similar to the form of the dispersion equation in an infinite film. The quantization effect of the spin-wave frequencies appears due to the finite dot radius and is essential for submicron magnetic dots. The discrete spin-wave frequencies are calculated in a practically important case of the square array of permalloy cylindrical dots. The relative intensities of spin-wave modes, when observed by Brillouin light scattering, are considered. The role of interdot dipole-dipole coupling is discussed.

Research paper thumbnail of Dynamics of coupled vortices in layered magnetic nanodots

Applied Physics Letters, 2005

The spin dynamics are calculated for a model system consisting of magnetically soft, layered nano... more The spin dynamics are calculated for a model system consisting of magnetically soft, layered nanomagnets, in which two ferromagnetic (F) cylindrical dots, each with a magnetic vortex ground state, are separated by a non-magnetic spacer (N). This permits a study of the effects of interlayer magnetostatic interactions on the vortex dynamics. The system was explored by applying the equations of motion for the vortex core positions. The restoring force was calculated taking into account the magnetostatic interactions assuming a realistic "surface charge free" spin distribution. For tri-layer F/N/F dots with opposite chiralities and the same core polarizations (lowest energy state), two eigenmodes are predicted analytically and confirmed via micromagnetic simulations. One mode is in the sub-GHz range for submicron dot diameters and corresponds to quasi-circular rotation of the cores about

Research paper thumbnail of Reorientational magnetic transition in high-density arrays of single-domain dots

Applied Physics Letters, 2000

A theoretical study on the reorientational transition from in-plane to out-of-plane magnetized st... more A theoretical study on the reorientational transition from in-plane to out-of-plane magnetized state is performed for two-dimensional magnetic dot arrays coupled by magnetostatic interaction. The square lattice of nanoscale cylindrical dots is considered with the assumptions that the dots are magnetically soft and they have uniform magnetization. The present study predicts that the interdot magnetostatic coupling determines the reorientation transition for close-packed arrays of such magnetic dots. Recent experimental results on the nanometer-scale single-domain dot arrays are discussed in light of the present calculation.

Research paper thumbnail of Low-frequency vortex dynamic susceptibility and relaxation in mesoscopic ferromagnetic dots

Applied Physics Letters, 2006

Vortex dynamics in a restricted geometry is considered for a magnetic system consisting of ferrom... more Vortex dynamics in a restricted geometry is considered for a magnetic system consisting of ferromagnetic cylindrical dots. To describe the vortex dynamic susceptibility and relaxation the equation of motion for the vortex center position is applied. The dependencies of the vortex dynamic susceptibility and resonance linewidth on geometrical parameters are calculated. A new method of extracting damping parameter from the vortex low-frequency resonance peaks is proposed and applied for interpretation of resonance data on FeNi circular dots.

Research paper thumbnail of Precise probing spin wave mode frequencies in the vortex state of circular magnetic dots

Applied Physics Letters, 2010

We report on detailed broadband ferromagnetic resonance measurements of azimuthal and radial spin... more We report on detailed broadband ferromagnetic resonance measurements of azimuthal and radial spin wave excitations in circular Permalloy dots in the vortex ground state. Dots with aspect ratio (β =height over radius) varied from 0.03 to 0.1 were explored. We found that for β exceeding approximately 0.05, variation of the spin wave eigenfrequencies with β deviates from the predicted ~ √β dependence. The frequency splitting of two lowest azimuthal modes was observed. The experimentally observed dependence of the frequency splitting on β was reasonably well described by dynamic splitting model accounting the spin-waves and, vortex gyrotropic mode interaction.

Research paper thumbnail of Shape effect on magnetization reversal in chains of interacting ferromagnetic elements

Applied Physics Letters, 2003

Research paper thumbnail of Acet, M. 142

Research paper thumbnail of IG-04 - Skyrmions in 3D soft magnetic nanodots with no Dzyaloshinskii-Moriya interactions

Abstract: Skyrmions typically appear in systems with perpendicular magnetic anisotropy (PMA) and ... more Abstract: Skyrmions typically appear in systems with perpendicular magnetic anisotropy (PMA) and Dzyaloshinskii-Moriya interactions (DMI). Bloch skyrmion states can be stabilized in magnetic dots with no need of DMI [1]. However, PMA is typically considered to be necessary. Nanoparticle geometry is an additional important factor for the skyrmion stabilization due to the influence of magnetostatic energy. Therefore, the sample shape (e.g. spherical) can result in stabilization of the skyrmions [2]. Recently, stabilization of the half-hedgehog skyrmions in soft magnetic (Permalloy) hemispherical dots by the MFM tip was demonstrated [3].<br/>Here we conduct micromagnetic simulations in 3D soft magnetic dots with planar (cylindrical) or curved (spherical cap) geometry with neither PMA nor DMI. The geometries of both magnetic elements correspond to the base radius 60-120 nm and the aspect ratio thickness/ radius ranged from 0.4 to 2 and magnetic parameters of permalloy. In a wide r...

Research paper thumbnail of Inertial Domain Wall Motion Driven by Staggered Spin-Orbit Fields in Uncompensated Antiferromagnets

Research paper thumbnail of Broadband communication and information processing with edge spin waves

Bulletin of the American Physical Society, 2019

El gobierno corporativo de las sociedades mercantiles y la protección de los accionistas minorita... more El gobierno corporativo de las sociedades mercantiles y la protección de los accionistas minoritarios José Mª López Jiménez Resumen: En este artículo se muestra la importancia de las disposiciones de gobierno corporativo en la gestión, especialmente, de las grandes sociedades de capital, y se identifican algunas medidas promovidas normativamente para fomentar la participación activa de los pequeños inversores, entre otros accionistas, en la vida de estas sociedades.

Research paper thumbnail of Half-hedgehog spin textures in sub-100 nm soft magnetic nanodots

Nanoscale, 2020

Permalloy hemispherical nanodots are able to host three-dimensional chiral structures (half-hedge... more Permalloy hemispherical nanodots are able to host three-dimensional chiral structures (half-hedgehog spin textures) with non-zero topological charge at room temperature and in absence of DMI interaction.

Research paper thumbnail of Effective dipolar boundary conditions for dynamic magnetization in thin magnetic stripes

Physical Review B, 2002

We show that dynamic magnetization at the lateral edges of a thin, axially magnetized magnetic el... more We show that dynamic magnetization at the lateral edges of a thin, axially magnetized magnetic element with finite in-plane size can be described by effective ''pinning'' boundary conditions. This effective pinning is of a purely dipolar nature, is not related to the magnetocrystalline surface anisotropy of the magnetic material, and is determined by the inhomogeneity of the dynamic demagnetizing field near the edges of the element. Eigenfunctions and eigenvalues obtained using these effective boundary conditions give quantitative description of the quantized spin wave spectra experimentally observed in long and thin permalloy stripes of a micron-size width.

Research paper thumbnail of Evolution and stability of a magnetic vortex in a small cylindrical ferromagnetic particle under applied field

Research paper thumbnail of Probing the Anharmonicity of the Potential Well for a Magnetic Vortex Core in a Nanodot

Physical Review Letters, 2013

Research paper thumbnail of Probing dynamical magnetization pinning in circular dots as a function of the external magnetic field orientation

Physical Review B, 2012

ABSTRACT We performed ferromagnetic resonance measurements of square arrays of noninteracting Per... more ABSTRACT We performed ferromagnetic resonance measurements of square arrays of noninteracting Permalloy circular dots for different orientations of external magnetic field with respect to the patterned film plane (θ). Out-of-plane angular dependence of the main resonance peak was measured in the whole range of the field angles 0° ⩽ θ ⩽ 90°. The main eigenmodespatial distribution is strongly nonuniform due to the dot nonellipsoidal shape. Nevertheless, for dots with small aspect ratio b=L/R⩽0.1 (where R is dot radius and L is dot thickness) Kittel&amp;#39;s equation, assuming uniform dynamic magnetization (no pinning at the dot lateral edges), describes the peak position with high accuracy. Analytical calculations and micromagnetic simulations confirmed the gradual evolution of the main mode profile and a smooth transition from the strong to relatively weak pinning conditions with the change of external magnetic field angle.

Research paper thumbnail of Quasiuniform magnetization state in soft ferromagnetic nanocylinders

Research paper thumbnail of Localized domain-wall excitations in patterned magnetic dots probed by broadband ferromagnetic resonance

Physical Review B, 2011

We investigate the magnetization dynamics in circular Permalloy dots with spatially separated mag... more We investigate the magnetization dynamics in circular Permalloy dots with spatially separated magnetic vortices interconnected by domain walls (double vortex state). We identify a novel type of quasi one-dimensional (1D) localised spin wave modes confined along domain walls, connecting each of two vortex cores with two edge half-antivortices. Variation of the mode eigenfrequencies with the dot size is in quantitative agreement with the developed model, which considers a dipolar origin of the localized 1D spin waves or so-called Winter´s magnons [J.M. Winter, Phys.Rev. 124, 452 (1961)]. These spin waves are analogous to the displacement waves of strings, and could be excited in a wide class of patterned magnetic nanostructures possessing domain walls, namely in triangular, square, circular or elliptic magnetic dots.

Research paper thumbnail of Stability of magnetic vortex in soft magnetic nano-sized circular cylinder

Journal of Magnetism and Magnetic Materials, 2002

Stability of magnetic vortex with respect to displacement of its center in a nano-scale circular ... more Stability of magnetic vortex with respect to displacement of its center in a nano-scale circular cylinder made of soft ferromagnetic material is studied theoretically. The mode of vortex displacement producing no magnetic charges on the cylinder side is proposed and the corresponding absolute single-domain radius of the cylinder is calculated as a function of its thickness and the exchange length of the material. In cylinders with the radii less than the single-domain radius the vortex state is unstable and is absolutely prohibited (except if pinned by material imperfections), so that the distribution of the magnetization vector in such cylinders in no applied magnetic field is uniform (or quasi-uniform). The phase diagram of nano-scale cylinders including the stability line and the metastability region obtained here is presented.

Research paper thumbnail of Multiscale versus micromagnetic calculations of the switching field reduction in FePt∕FeRh bilayers with perpendicular exchange spring

Journal of Applied Physics, 2005

Calculations of magnetisation reversal via a perpendicular exchange spring in soft-hard bilayers ... more Calculations of magnetisation reversal via a perpendicular exchange spring in soft-hard bilayers are presented using the example of an FePt/ FeRh bilayer which has recently been proposed as an alternative medium for heat-assisted magnetic recording applications. We show that the standard three-dimensional micromagnetic model fails to describe the coercivity reduction due to the fact that at low interface exchange value, the domain wall penetration into the hard layer is not correctly described within the continuous approach. A multiscale model based on atomic level simulations near the interface and a micromagnetic approach far from it is proposed. This leads to improved calculations of the exchange spring at the interface, allowing a detailed study of the magnetisation reversal dynamics. As a result, the coercivity is found to saturate at an interfacial exchange value of 4% of the bulk value, the practical applications of which are discussed. In addition, the granular structure in an FePt medium with different intergrain exchange parameters is considered.

Research paper thumbnail of Spin-waves in cylindrical magnetic dot arrays with in-plane magnetization

Journal of Applied Physics, 2000

The discrete spectrum of dipole-exchange spin-wave modes of a tangentially magnetized cylindrical... more The discrete spectrum of dipole-exchange spin-wave modes of a tangentially magnetized cylindrical magnetic dot is calculated from the solution of the Landau-Lifshitz equation and the magnetostatic Maxwell equations in a cylindrical geometry. The general surface spin-pinning conditions at the radial dot boundary are considered. The main simplifying assumptions are: ͑i͒ the dot radius is much larger than the dot height; ͑ii͒ the distribution of the variable magnetization along the dot height is uniform. The approximate dispersion equation for spin-wave modes in a dot is obtained in a simple analytical form similar to the form of the dispersion equation in an infinite film. The quantization effect of the spin-wave frequencies appears due to the finite dot radius and is essential for submicron magnetic dots. The discrete spin-wave frequencies are calculated in a practically important case of the square array of permalloy cylindrical dots. The relative intensities of spin-wave modes, when observed by Brillouin light scattering, are considered. The role of interdot dipole-dipole coupling is discussed.

Research paper thumbnail of Spin-waves in cylindrical magnetic dot arrays with in-plane magnetization

Journal of Applied Physics, 2000

The discrete spectrum of dipole-exchange spin-wave modes of a tangentially magnetized cylindrical... more The discrete spectrum of dipole-exchange spin-wave modes of a tangentially magnetized cylindrical magnetic dot is calculated from the solution of the Landau-Lifshitz equation and the magnetostatic Maxwell equations in a cylindrical geometry. The general surface spin-pinning conditions at the radial dot boundary are considered. The main simplifying assumptions are: ͑i͒ the dot radius is much larger than the dot height; ͑ii͒ the distribution of the variable magnetization along the dot height is uniform. The approximate dispersion equation for spin-wave modes in a dot is obtained in a simple analytical form similar to the form of the dispersion equation in an infinite film. The quantization effect of the spin-wave frequencies appears due to the finite dot radius and is essential for submicron magnetic dots. The discrete spin-wave frequencies are calculated in a practically important case of the square array of permalloy cylindrical dots. The relative intensities of spin-wave modes, when observed by Brillouin light scattering, are considered. The role of interdot dipole-dipole coupling is discussed.

Research paper thumbnail of Dynamics of coupled vortices in layered magnetic nanodots

Applied Physics Letters, 2005

The spin dynamics are calculated for a model system consisting of magnetically soft, layered nano... more The spin dynamics are calculated for a model system consisting of magnetically soft, layered nanomagnets, in which two ferromagnetic (F) cylindrical dots, each with a magnetic vortex ground state, are separated by a non-magnetic spacer (N). This permits a study of the effects of interlayer magnetostatic interactions on the vortex dynamics. The system was explored by applying the equations of motion for the vortex core positions. The restoring force was calculated taking into account the magnetostatic interactions assuming a realistic "surface charge free" spin distribution. For tri-layer F/N/F dots with opposite chiralities and the same core polarizations (lowest energy state), two eigenmodes are predicted analytically and confirmed via micromagnetic simulations. One mode is in the sub-GHz range for submicron dot diameters and corresponds to quasi-circular rotation of the cores about

Research paper thumbnail of Reorientational magnetic transition in high-density arrays of single-domain dots

Applied Physics Letters, 2000

A theoretical study on the reorientational transition from in-plane to out-of-plane magnetized st... more A theoretical study on the reorientational transition from in-plane to out-of-plane magnetized state is performed for two-dimensional magnetic dot arrays coupled by magnetostatic interaction. The square lattice of nanoscale cylindrical dots is considered with the assumptions that the dots are magnetically soft and they have uniform magnetization. The present study predicts that the interdot magnetostatic coupling determines the reorientation transition for close-packed arrays of such magnetic dots. Recent experimental results on the nanometer-scale single-domain dot arrays are discussed in light of the present calculation.

Research paper thumbnail of Low-frequency vortex dynamic susceptibility and relaxation in mesoscopic ferromagnetic dots

Applied Physics Letters, 2006

Vortex dynamics in a restricted geometry is considered for a magnetic system consisting of ferrom... more Vortex dynamics in a restricted geometry is considered for a magnetic system consisting of ferromagnetic cylindrical dots. To describe the vortex dynamic susceptibility and relaxation the equation of motion for the vortex center position is applied. The dependencies of the vortex dynamic susceptibility and resonance linewidth on geometrical parameters are calculated. A new method of extracting damping parameter from the vortex low-frequency resonance peaks is proposed and applied for interpretation of resonance data on FeNi circular dots.

Research paper thumbnail of Precise probing spin wave mode frequencies in the vortex state of circular magnetic dots

Applied Physics Letters, 2010

We report on detailed broadband ferromagnetic resonance measurements of azimuthal and radial spin... more We report on detailed broadband ferromagnetic resonance measurements of azimuthal and radial spin wave excitations in circular Permalloy dots in the vortex ground state. Dots with aspect ratio (β =height over radius) varied from 0.03 to 0.1 were explored. We found that for β exceeding approximately 0.05, variation of the spin wave eigenfrequencies with β deviates from the predicted ~ √β dependence. The frequency splitting of two lowest azimuthal modes was observed. The experimentally observed dependence of the frequency splitting on β was reasonably well described by dynamic splitting model accounting the spin-waves and, vortex gyrotropic mode interaction.

Research paper thumbnail of Shape effect on magnetization reversal in chains of interacting ferromagnetic elements

Applied Physics Letters, 2003

Research paper thumbnail of Acet, M. 142