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Giant moving vortex mass in thick magnetic nanodots.

Guslienko KY, Kakazei GN, Ding J, Liu XM, Adeyeye AO - Sci Rep (2015)

Bottom Line: Magnetic vortex is one of the simplest topologically non-trivial textures in condensed matter physics.The vortex mass depends on the system geometry and is non-local because of important role of the dipolar interaction.However, its importance increases drastically with the dot thickness increasing.

View Article: PubMed Central - PubMed

Affiliation: Depto. Física de Materiales, Universidad del País Vasco, UPV/EHU, 20018 San Sebastián, Spain.

ABSTRACT
Magnetic vortex is one of the simplest topologically non-trivial textures in condensed matter physics. It is the ground state of submicron magnetic elements (dots) of different shapes: cylindrical, square etc. So far, the vast majority of the vortex dynamics studies were focused on thin dots with thickness 5-50 nm and only uniform across the thickness vortex excitation modes were observed. Here we explore the fundamental vortex mode in relatively thick (50-100 nm) dots using broadband ferromagnetic resonance and show that dimensionality increase leads to qualitatively new excitation spectra. We demonstrate that the fundamental mode frequency cannot be explained without introducing a giant vortex mass, which is a result of the vortex distortion due to interaction with spin waves. The vortex mass depends on the system geometry and is non-local because of important role of the dipolar interaction. The mass is rather small for thin dots. However, its importance increases drastically with the dot thickness increasing.

No MeSH data available.


Related in: MedlinePlus

The frequency of the lowest vortex gyrotropic mode vs. dot thickness,ω0(L) 2p: red squares – theexperimental data, blue solid line – the simulated frequencies, greensolid line – the calculations according to Eq. (4)accounting vortex mass, black dashed line – calculations withoutaccounting for the vortex mass.Inset: the dependence of the vortex mass density on the dot thickness calculated by using Eq.(9).
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f3: The frequency of the lowest vortex gyrotropic mode vs. dot thickness,ω0(L) 2p: red squares – theexperimental data, blue solid line – the simulated frequencies, greensolid line – the calculations according to Eq. (4)accounting vortex mass, black dashed line – calculations withoutaccounting for the vortex mass.Inset: the dependence of the vortex mass density on the dot thickness calculated by using Eq.(9).

Mentions: The microwave absorption of the dot arrays was probed using a vector networkanalyzer by sweeping the frequency in 50 MHz −6 GHzrange in the absence of an external magnetic field at room temperature. Themicrowave field, hrf, is oscillating in the patterned filmplane perpendicularly to the central waveguide (Fig. 2).The measured microwave excitation spectra are quite complicated. Therefore, weconcentrated our attention on the lowest resonance peak that was clearlyobserved in the vicinity of 1 GHz. This peak was interpreted as thevortex gyrotropic mode, which is almost uniform (i.e., its dynamicalmagnetization profile has no nodes) along the dot thickness1415. A careful measurements of the dependence of resonance frequency of this modeon the dot thickness demonstrate a clear maximum around the dot thicknessL = 70 nm (see Fig.3).


Giant moving vortex mass in thick magnetic nanodots.

Guslienko KY, Kakazei GN, Ding J, Liu XM, Adeyeye AO - Sci Rep (2015)

The frequency of the lowest vortex gyrotropic mode vs. dot thickness,ω0(L) 2p: red squares – theexperimental data, blue solid line – the simulated frequencies, greensolid line – the calculations according to Eq. (4)accounting vortex mass, black dashed line – calculations withoutaccounting for the vortex mass.Inset: the dependence of the vortex mass density on the dot thickness calculated by using Eq.(9).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4565097&req=5

f3: The frequency of the lowest vortex gyrotropic mode vs. dot thickness,ω0(L) 2p: red squares – theexperimental data, blue solid line – the simulated frequencies, greensolid line – the calculations according to Eq. (4)accounting vortex mass, black dashed line – calculations withoutaccounting for the vortex mass.Inset: the dependence of the vortex mass density on the dot thickness calculated by using Eq.(9).
Mentions: The microwave absorption of the dot arrays was probed using a vector networkanalyzer by sweeping the frequency in 50 MHz −6 GHzrange in the absence of an external magnetic field at room temperature. Themicrowave field, hrf, is oscillating in the patterned filmplane perpendicularly to the central waveguide (Fig. 2).The measured microwave excitation spectra are quite complicated. Therefore, weconcentrated our attention on the lowest resonance peak that was clearlyobserved in the vicinity of 1 GHz. This peak was interpreted as thevortex gyrotropic mode, which is almost uniform (i.e., its dynamicalmagnetization profile has no nodes) along the dot thickness1415. A careful measurements of the dependence of resonance frequency of this modeon the dot thickness demonstrate a clear maximum around the dot thicknessL = 70 nm (see Fig.3).

Bottom Line: Magnetic vortex is one of the simplest topologically non-trivial textures in condensed matter physics.The vortex mass depends on the system geometry and is non-local because of important role of the dipolar interaction.However, its importance increases drastically with the dot thickness increasing.

View Article: PubMed Central - PubMed

Affiliation: Depto. Física de Materiales, Universidad del País Vasco, UPV/EHU, 20018 San Sebastián, Spain.

ABSTRACT
Magnetic vortex is one of the simplest topologically non-trivial textures in condensed matter physics. It is the ground state of submicron magnetic elements (dots) of different shapes: cylindrical, square etc. So far, the vast majority of the vortex dynamics studies were focused on thin dots with thickness 5-50 nm and only uniform across the thickness vortex excitation modes were observed. Here we explore the fundamental vortex mode in relatively thick (50-100 nm) dots using broadband ferromagnetic resonance and show that dimensionality increase leads to qualitatively new excitation spectra. We demonstrate that the fundamental mode frequency cannot be explained without introducing a giant vortex mass, which is a result of the vortex distortion due to interaction with spin waves. The vortex mass depends on the system geometry and is non-local because of important role of the dipolar interaction. The mass is rather small for thin dots. However, its importance increases drastically with the dot thickness increasing.

No MeSH data available.


Related in: MedlinePlus