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<10 ns followed by logarithmic decay for tp>10 ns, 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 τn = τ0≈5 ns.
Citation: Physical Review Letters
Pub Type: Journals