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Light Used as a Magnetic Hammer

Scientists in the University of Nebraska MRSEC are using very short light pulses from a femtosecond laser to perturb magnetic materials and to probe their behavior at times after the perturbation. The light pulses are only about 100 millionth-billionths of a second long.

When the "pump" pulse strikes the sample, it acts like a magnetic hammer to quickly change the direction that the magnetization M points. M then spins around (precesses) very rapidly. The much weaker "probe" pulse comes along a short time later and measures the direction in which M points.

By adjusting the delay time between the pump and probe pulses, we get a detailed picture of how the magnetization precesses with time. These investigations provide information that is useful in such applications as magnetic information storage on hard disk drives.

Light Used as a Magnetic Hammer

N. I. Polushkin, S. A. Michalski, L. Yue, R. D. Kirby, Phys. Rev. Lett. 97, 256401 (2006).