Spin dynamics and damping in nanomagnets measured directly by frequency-resolved magneto-optic Kerr effect

The spin dynamics of sub-100-nm Ni80Fe20 nanomagnets are directly measured using the magneto-optic Kerr effect and a broadband detection scheme. Elliptical dots approximately 68nm in diameter and 10nm thick were fabricated in 20×20μm2 arrays. There is approximately a factor of 2 increase in the effective linewidth when compared to a 20μm diameter continuous disk of the same material. Using micromagnetic simulations, we model the effect of dot-to-dot size variation on the effective linewidth and find that 2nm size variations are more than sufficient to account for the effective increase in linewidth.