Effect of interlayer exchange coupling in spin-torque nano oscillator

The dynamics of the magnetization of the free layer in a spin-torque nano oscillator (STNO) influenced by a noncollinear alignment between the magnetizations of the free and pinned layers due to an interlayer exchange coupling has been investigated theoretically. The orientations of the magnetization of the free layer with that of the pinned layer have been computed through the macrospin model and they are found to match well with experimental results. The bilinear and biquadratic coupling strengths make the current to switch the magnetization between two states or oscillate steadily. The expressions for the critical currents between which oscillations are possible and the critical bilinear coupling strength below which oscillations are not possible are derived. The frequency of the oscillations is shown to be tuned and increased to or above 300 GHz by the current, which is the largest to date among nanopillar-shaped STNOs.

Automated summary

The dynamics of the magnetization of the free layer in a spin-torque nano oscillator influenced by a noncollinear alignment between the magnetizations of the free and pinned layers has been studied. The computed orientations of the magnetization match well with experimental results. Bilinear and biquadratic coupling strengths allow for magnetization switching or steady oscillations. Expressions for the critical currents and coupling strength have been derived. The frequency of oscillations can be tuned and increased to above 300 GHz, the highest among nanopillar-shaped STNOs.