Magnetization switching by microwaves initially rotating in opposite direction to precession

Taniguchi, Tomohiro

doi:10.7567/apex.8.123002

Cited by 4 publications

(2 citation statements)

References 28 publications

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“…Usually, such microwaves are inefficient for switching because the switched state becomes energetically unstable. It was recently shown, however, that such microwaves result in the switching when the frequency depends on time [64].…”

Section: B Competition Between Spin Torque and Microwavesmentioning

confidence: 99%

Magnetization switching by current and microwaves

2016

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We propose a theoretical model of magnetization switching in a ferromagnetic multilayer by both electric current and microwaves. The electric current gives a spin transfer torque on the magnetization, while the microwaves induce a precession of the magnetization around the initial state. Based on numerical simulation of the Landau-Lifshitz-Gilbert (LLG) equation, it is found that the switching current is significantly reduced compared with the switching caused solely by the spin transfer torque when the microwave frequency is in a certain range. We develop a theory of switching from the LLG equation averaged over a constant energy curve. It was found that the switching current should be classified into four regions, depending on the values of the microwave frequency. Based on the analysis, we derive an analytical formula of the optimized frequency minimizing the switching current, which is smaller than the ferromagnetic resonance frequency. We also derive an analytical formula of the minimized switching current. Both the optimized frequency and the minimized switching current decrease with increasing the amplitude of the microwave field. The results will be useful to achieve high thermal stability and low switching current in spin torque systems simultaneously.

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Section: B Competition Between Spin Torque and Microwavesmentioning

confidence: 99%

Magnetization switching by current and microwaves

2016

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“…It has been proposed in the field of magnetic recording that the oscillating magnetic field emitted from the spin torque oscillator is useful to reduce the magnitude of the writing magnetic field of high-density magnetic recording media. The method of this magnetization switching is called microwave assisted magnetization reversal (MAMR) or microwave assisted magnetization switching (MAS) [20,24,25,29,31,32,51,52,53,54,55,56]. The magnitude of the magnetic field emitted from the spin torque oscillator determines the writing magnetic field in MAMR [57,58].…”

Section: Applicationmentioning

confidence: 99%

An analytical computation of magnetic field generated from a cylinder ferromagnet

Taniguchi

2018

Journal of Magnetism and Magnetic Materials

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An analytical formulation to compute a magnetic field generated from an uniformly magnetized cylinder ferromagnet is developed. Exact solutions of the magnetic field generated from the magnetization pointing in an arbitrary direction are derived, which are applicable both inside and outside the ferromagnet. The validities of the present formulas are confirmed by comparing them with demagnetization coefficients estimated in earlier works. The results will be useful for designing practical applications, such as high-density magnetic recording and microwave generators, where nanostructured ferromagnets are coupled to each other through the dipole interactions and show cooperative phenomena such as synchronization. As an example, the magnetic field generated from a spin torque oscillator for magnetic recording based on microwave assisted magnetization reversal is studied.

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