Effect of nonuniform perpendicular anisotropy in ferromagnetic resonance spectra in magnetic nanorings

AbstractThe high frequency dynamic behaviors of magnetic nanorings with variable anisotropy along their radius have been studied using micromagnetic simulations. The dynamic susceptibility spectrum and spatial localization of the ferromagnetic resonance modes are investigated by varying anisotropy gradients in nanorings of 200 nm of external radius, with different internal radii. Both the resonant frequencies and the number of peaks depend on the lower energy magnetization configuration which in turn is a function of anisotropy gradients. Besides, it is shown that the effects of the anisotropy gradient are relevant even for the narrowest ring of 10 nm wide. The idea of controlling frequencies by modifying the anisotropy gradients of the system suggests the possibility of using these nanostructures in potential magnetic controllable frequency devices.

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Analysis of Plasma Properties and Deposition of Amorphous Silicon Alloy Solar Cells Using Very High Frequency Glow Discharge

MRS Proceedings ◽

10.1557/proc-557-115 ◽

1999 ◽

Vol 557 ◽

Cited By ~ 19

Author(s):

B. Yan ◽

J. Yang ◽

S. Guha ◽

A. Gallagher

Keyword(s):

Solar Cells ◽

High Frequency ◽

Lower Energy ◽

Ionic Current ◽

Ion Bombardment ◽

Half Width ◽

Rf Plasma ◽

Very High Frequency ◽

Very High ◽

Ionic Energy

AbstractPositive ionic energy distributions in modified very-high-frequency (MVHF) and radio frequency (RF) glow discharges were measured using a retarding field analyzer. The ionic energy distribution for H2 plasma with 75 MHz excitation at a pressure of 0.1 torr has a peak at 22 eV with a half-width of about 6 eV. However, with 13.56 MHz excitation, the peak appears at 37 eV with a much broader half-width of 18 eV. The introduction of SiH4 to the plasma shifts the distribution to lower energy. Increasing the pressure not only shifts the distribution to lower energy but also broadens the distribution. In addition, the ionic current intensity to the substrate is about five times higher for MVHF plasma than for RF plasma. In order to study the effect of ion bombardment, the deposition of a-Si alloy solar cells using MVHF was investigated in detail at different pressures and external biases. Lowering the pressure and negatively biasing the substrate increases ion bombardment energy and results in a deterioration of cell performance. It indicates that ion bombardment is not beneficial for making solar cells using MVHF. By optimizing the deposition conditions, a 10.8% initial efficiency of a-Si/a-SiGe/SiGe triple-junction solar cell was achieved at a deposition rate of 0.6 nm/sec.

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High perpendicular anisotropy in sub-30 nm MRAM devices measured by spin-torque ferromagnetic resonance

2017 IEEE International Magnetics Conference (INTERMAG) ◽

10.1109/intmag.2017.8007703 ◽

2017 ◽

Cited By ~ 1

Author(s):

L. Thomas ◽

G. Jan ◽

S. Serrano-Guisan ◽

S. Le ◽

J. Iwata-Harms ◽

...

Keyword(s):

Ferromagnetic Resonance ◽

Spin Torque ◽

Perpendicular Anisotropy

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Difference between Brownian and Néel relaxation mechanisms in a magnetizing field

ВЕСТНИК ПЕРМСКОГО УНИВЕРСИТЕТА ФИЗИКА ◽

10.17072/1994-3598-2021-4-14-20 ◽

2021 ◽

pp. 14-20

Author(s):

Alexander V. Lebedev ◽

Keyword(s):

Relaxation Time ◽

Oleic Acid ◽

High Frequency ◽

Cobalt Ferrite ◽

Magnetic Moments ◽

Relaxation Mechanism ◽

Dynamic Susceptibility ◽

Magnetite Particles ◽

Magnetizing Field ◽

Néel Relaxation

Measurements of the dynamic susceptibility of a magnetic fluid based on cobalt ferrite particles stabilized in water by a double surfactant layer have been carried out. Cobalt ferrite, in comparison with magnetite, has a significantly higher energy of magnetic anisotropy. Therefore, for particles of cobalt ferrite, the Brownian mechanism of relaxation of magnetic moments is characteristic. The Debye (with a finite relaxation time) contribution to the dynamic susceptibility and the high-frequency (dispersionless) contribution are distinguished by constructing Cole-Cole diagrams. It was found that with an increase in the magnetizing field, the Debye contribution to the dynamic susceptibility decreases, while the high-frequency one (having a zero relaxation time) remains unchanged. The indicated property of the dynamic susceptibility of a fluid with a Brownian relaxation mechanism is radically different from the properties of the susceptibility of a fluid with Néel particles. Previously, measurements were made of the susceptibility of a fluid based on magnetite particles stabilized with oleic acid in kerosene. The magnetite particles have significantly lower anisotropy energy and are characterized by the predominance of the Néel relaxation mechanism. Turning on the magnetizing field caused a decrease in both the Debye part of the susceptibility and the high-frequency part of the susceptibility of magnetite particles.

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Magnetization switching assisted by high-frequency-voltage-induced ferromagnetic resonance

Applied Physics Express ◽

10.7567/apex.7.073002 ◽

2014 ◽

Vol 7 (7) ◽

pp. 073002 ◽

Cited By ~ 19

Author(s):

Takayuki Nozaki ◽

Hiroko Arai ◽

Kay Yakushiji ◽

Shingo Tamaru ◽

Hitoshi Kubota ◽

...

Keyword(s):

Ferromagnetic Resonance ◽

High Frequency ◽

Magnetization Switching

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High frequency microwave on-chip inductors using increased ferromagnetic resonance frequency of magnetic films

2015 28th IEEE International Conference on Micro Electro Mechanical Systems (MEMS) ◽

10.1109/memsys.2015.7050923 ◽

2015 ◽

Cited By ~ 4

Author(s):

Kisik Koh ◽

Donald S. Gardner ◽

Chen Yang ◽

Kevin P. O'brien ◽

Noureddine Tayebi ◽

...

Keyword(s):

Resonance Frequency ◽

Ferromagnetic Resonance ◽

High Frequency ◽

Magnetic Films ◽

On Chip ◽

Ferromagnetic Resonance Frequency ◽

High Frequency Microwave

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High ferromagnetic resonance and thermal stability spinel Ni0.7Mn0.3−xCoxFe2O4 ferrite for ultra high frequency devices

Journal of Applied Physics ◽

10.1063/1.3678300 ◽

2012 ◽

Vol 111 (7) ◽

pp. 07A516 ◽

Cited By ~ 2

Author(s):

Jaejin Lee ◽

Yang-Ki Hong ◽

Woncheol Lee ◽

Gavin S. Abo ◽

Jihoon Park ◽

...

Keyword(s):

Thermal Stability ◽

Ferromagnetic Resonance ◽

High Frequency ◽

Ultra High Frequency ◽

High Frequency Devices

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Structural Improvement of the ω-Type High-Speed Rail Clip Based on a Study of Its Failure Mechanism

Shock and Vibration ◽

10.1155/2019/4127065 ◽

2019 ◽

Vol 2019 ◽

pp. 1-14 ◽

Cited By ~ 1

Author(s):

Xiaogang Gao ◽

Anbin Wang ◽

Yu He ◽

Xiaohan Gu

Keyword(s):

Failure Mechanism ◽

Fatigue Test ◽

High Frequency ◽

High Speed ◽

Excitation Frequency ◽

Test System ◽

Vibration Measurement ◽

High Speed Rail ◽

Resonant Frequencies ◽

Rail Wear

In the circumstances of high-speed railways, the wheel-rail vibration is significantly aggravated by polygonal wheel wear and rail corrugation, which subsequently leads to the wheel-rail interaction at higher frequencies and potential failure of the rail fastening. In this paper, a ω-type clip of the fastening in the CRH high-speed rail was used to investigate the failure mechanism. First, a dynamic wheel-rail coupling model and a finite element analysis of the rail clip were developed, from which the rail vibration frequency and modal frequencies of the clip with different installation torques were obtained. The experimental tests and modal simulation results were mutually verified. In addition, the real-time vibration measurement and the wheel-rail wear monitoring were carried out at a CRH high-speed railway site. It was found that the resonant frequencies of the ω-type clip in the installation condition coincided with the excitation frequencies of the wheel-rail interaction induced by wheel-rail wear. The high-frequency dynamic failure mechanism of a typical ω-type clip, W300-1, is put forward for the first time. Moreover, a high-frequency rail clip fatigue test system was designed and developed specifically for this study. The loading excitation frequency of the clip test used was set as 590 Hz, and the loading amplitude was 0.05 mm. After 125-minute operation of the test system, the clip was broken at the expected location predicted by the FEA model. The high-frequency fatigue test result further verified that the failure mechanism of the ω-type clip was due to the resonance of the clip with its excitation force from the wheel-rail interaction. Finally, the clip was then structurally improved taking into account the stiffness and mass, which led to its resonant frequencies shifting away from the high-frequency excitation range, hence avoiding resonance failure of the subject clip.

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