Instability analysis of spin torque oscillator with an in-plane magnetized free layer and a perpendicularly magnetized pinned layer

Abstract

We study the theoretical conditions to excite a stable self-oscillation in a spin torque oscillator with an in-plane magnetized free layer and a perpendicularly magnetized pinned layer in the presence of magnetic field pointing in an arbitrary direction. The linearized Landau-Lifshitz-Gilbert (LLG) equation is found to be inapplicable to evaluate the threshold between the stable and self-oscillation states because the critical current density estimated from the linearized equation is considerably larger than that found in the numerical simulation. We derive a theoretical formula of the threshold current density by focusing on the energy gain of the magnetization from the spin torque during a time shorter than a precession period. A good agreement between the derived formula and the numerical simulation is obtained. The condition to stabilize the out-of-plane self-oscillation above the threshold is also discussed.

13 pages, 6 figures

References in corpus (5)

• Spin-torque switching: Fokker-Planck rate calculation
• Spin torque switching of an in-plane magnetized system in a thermally activated region
• Magnetization reversal condition for a nanomagnet within a rotating magnetic field
• Spin Torque Oscillators with Thermal Noise: A Constant Energy Orbit Approach
• Nonlinear analysis of magnetization dynamics excited by spin Hall effect

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