Relaxation Times for Magnetization Reversal in a High Coercivity Magnetic Thin Film

We used a magneto-optical Kerr effect microscope to measure 180^∘{} magnetization reversal in a high coercivity CoCr₁₀Ta₄ thin film subjected to nanosecond field pulses. Exponential magnetization decay occurs for pulse duration tₚ<100ex0exns followed by logarithmic decay for tₚ>100ex0exns, indicating a crossover from nonequilibrium magnetization relaxation at short tₚ to metastable equilibrium and thermal relaxation for longer tₚ. We conclude that the nonequilibrium magnetization relaxation time (τₙ) and that the average relaxation time of microscopic thermal fluctuations (τ₀) is τₙ0ex0ex=0ex0exτ₀≈5ns.