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- Muduli Kishor, Pranaba, 1978, et al.
(författare)
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Decoherence and Mode Hopping in a Magnetic Tunnel Junction Based Spin Torque Oscillator
- 2012
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Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 108:20, s. 207203-
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Tidskriftsartikel (refereegranskat)abstract
- We discuss the coherence of magnetic oscillations in a magnetic tunnel junction based spin torque oscillator as a function of the external field angle. Time-frequency analysis shows mode hopping between distinct oscillator modes, which arises from linear and nonlinear couplings in the Landau-Lifshitz-Gilbert equation, analogous to mode hopping observed in semiconductor ring lasers. These couplings and, therefore, mode hopping are minimized near the current threshold for the antiparallel alignment of free-layer with reference layer magnetization. Away from the antiparallel alignment, mode hopping limits oscillator coherence.
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| 2. |
- Muduli Kishor, Pranaba, 1978, et al.
(författare)
-
Temperature dependence of linewidth in nanocontact based spin torque oscillators : Effect of multiple oscillatory modes
- 2012
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 86:17, s. 174408-
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Tidskriftsartikel (refereegranskat)abstract
- We discuss the effect of mode transitions on the current (I) and temperature (T) dependent linewidth (Delta f) in nanocontact based spin torque oscillators (STOs). At constant I, Delta f exhibits an anomalous temperature dependence near the mode transitions; Delta f may either increase or decrease with T depending on the position w.r.t. the mode transition. We show that the behavior of Delta f as a function of I can be fitted by the single mode analytical theory of STOs, even though there are two modes present near the mode transition, if the nonlinear amplification is determined directly from the experiment. Using a recently developed theory of two coupled modes, we show that the linewidth near mode transition can be described by an "effective" single-oscillator theory with an enhanced nonlinear amplification that carries additional temperature dependence, which thus qualitatively explain the experimental results.
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