Intrinsic and Thermal Linewidths of Spin-Transfer-Driven Vortex Self-Oscillations

Narrow linewidth spin transfer driven vortex self-oscillations in Py/Cu/Py spin valves of elliptical cross section (160 nm × 75 nm) are investigated by means of micromagnetic simulations. “GPmagnet”, a high performance GPU based micromagnetic package, is used for this purpose, allowing for 100 KHz spectral resolution at reasonable computational time. The variation of the linewidth with applied current (10 × 10⁷ A/cm² A/cm² <; J <; 20 × 10⁷ A/cm²) is analyzed in the temperature range 0 K <; K <; 300 K. Linewidths around 1 MHz are found at T = 0K. At T = 300 K, linewidths remain below 2 MHz for J <; 16 × 10⁷ A/cm², whereas for larger currents the presence of two oscillation modes lead to a further linewidth increase.