Helen Gomonay, Vadim Loktev
Spin-torque effects in antiferromagnetic (AFM) materials are of great interest because of the possible applications as high-speed spintronic devices. In the present paper we analyze the statistical properties of the current-driven AFM nanooscillator that result from the white Gaussian noise of magnetic nature. Starting from the peculiarities of deterministic dynamics we derive Langevin and Fokker-Planck equations in energy representation for two normal modes. We find the stationary distribution function in the subcritical and overcritical regimes and calculate the current dependence of average energy, energy fluctuation and their ratio (quality factor). It is found that one of the modes (noncritical) shows the Boltzmann statistics with current-dependent effective temperature in all range of current values. The effective temperature of the other (soft) mode critically depends on current in the subcritical region. Distribution function of soft mode follows the Gaussian law above the generation threshold. In the overcritical regime the full average energy and quality factor grow with current value that makes AFM nanooscillators promising candidates as active spintronic components.
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http://arxiv.org/abs/1207.4344
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