Microwave assisted switching mechanism and its stable switching limit

Okamoto, Satoshi; Igarashi, M.; Kikuchi, Nobuaki; Kitakami, Osamu

doi:10.1063/1.3436570

Cited by 49 publications

(51 citation statements)

References 27 publications

(29 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Large angle precession induced by the microwave field is not observed in the early stage of the magnetization switching in the unstable switching region for condition (a). On the other hand, magnetization switching through a quasiperiodic magnetization mode [21] was observed under condition (b), which was also been demonstrated elsewhere [14]. Magnetization was also confirmed to switch through a pure time-harmonic magnetization mode with no generation of higher-order harmonics (P-mode) in the stable switching region (c).…”

Section: Resultssupporting

confidence: 74%

Stable microwave-assisted magnetization switching for nanoscale exchange-coupled composite grain

et al. 2013

View full text Add to dashboard Cite

Magnetization mechanisms of nanoscale magnetic grains greatly differ from well-known magnetization mechanisms of micrometer- or millimeter-sized magnetic grains or particles. Magnetization switching mechanisms of nanoscale exchange-coupled composite (ECC) grain in a microwave field was studied using micromagnetic simulation. Magnetization switching involving a strongly damped or precessional oscillation was studied using various strengths of external direct current and microwave fields. These studies imply that the switching behavior of microwave-assisted magnetization switching of the ECC grain can be divided into two groups: stable and unstable regions, similar to the case of the Stoner-Wahlfarth grain. A significant reduction in the switching field was observed in the ECC grain when the magnetization switching involved precessional oscillations similar to the case of the Stoner-Wohlfarth grain. This switching behavior is preferred for the practical applications of microwave-assisted magnetization switching.

show abstract

Section: Resultssupporting

confidence: 74%

Stable microwave-assisted magnetization switching for nanoscale exchange-coupled composite grain

et al. 2013

View full text Add to dashboard Cite

show abstract

“…This is attributable to the appearance of a metastable resonant motion that does not easily assist the magnetization reversal. 25 From Figs. 3(b) and 3(c), the effect of the rf field on the non-uniform rotation of the magnetization can also be discussed.…”

Section: Astroid Curves Under Applied Rf Fieldmentioning

confidence: 96%

Frequency dependence of critical switching asteroid of CoCrPt–SiO2 granular film under 50-ns microwave impulse

Ishida¹,

Soeno²,

Sekiguchi³

et al. 2013

Journal of Applied Physics

View full text Add to dashboard Cite

Understanding the dynamic process of microwave-assisted magnetization reversal (MAMR) in a dipole–dipole coupled granular perpendicular medium is essential for its application to future magnetic storage devices. We experimentally investigated the magnetization reversal process in CoCrPt–SiO2 granular films in terms of the dependence of the switching field on the strength of an applied in-plane radio-frequency magnetic field. The reversal process changed from non-uniform rotation to uniform rotation when the frequency increased toward the ferromagnetic resonance frequency. In the resonant condition, the switching field agreed well with a model assuming uniform rotation of the magnetization in each grain. The agreement suggests that the decoherence of ferromagnetic resonance due to a dynamic dipolar field is weak in adequately exchange-coupled granular films with a saturation magnetization of 415 emu/cm3. This finding is significant for the development of the practical medium necessary for MAMR writing.

show abstract

“…On the other hand, in microwave-assisted magnetization reversal, microwaves with frequencies on the order of the ferromagnetic resonance (FMR) frequency efficiently supply energy to the ferromagnet, and reduce the direct field for switching. Typically, the switching field is reduced by less than half of the anisotropy field [20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36].…”

Section: Introductionmentioning

confidence: 99%

Magnetization switching by current and microwaves

2016

View full text Add to dashboard Cite

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.

show abstract

Microwave assisted switching mechanism and its stable switching limit

Cited by 49 publications

References 27 publications

Stable microwave-assisted magnetization switching for nanoscale exchange-coupled composite grain

Stable microwave-assisted magnetization switching for nanoscale exchange-coupled composite grain

Frequency dependence of critical switching asteroid of CoCrPt–SiO2 granular film under 50-ns microwave impulse

Magnetization switching by current and microwaves

Contact Info

Product

Resources

About