Spatially Resolved Dynamics of Localized Spin-Wave Modes in Ferromagnetic Wires. How fast can the bits that store information on a hard drive be rewritten? This is one of the questions being addressed by the Magnetic Heterostructures IRG using a technique in which "movies"of magnetic processes are recorded on time scales less than 100 picoseconds (a picosecond is one-tenth of one-billionth of a second) and with spatial resolution less than one micron. Park and co-workers have used this technique to observe magnetic excitations that are confined to regions near the edges of thin magnetic strips. These "localized spin waves" are analogous to the standing waves of a guitar string. In this case, the length of the "string" is less than one micron and is determined by an applied magnetic field. Further work in the IRG is devoted to studying switching processes in even smaller systems, with sizes below one micron. [J. P. Park, P. Eames, D. M. Engebretson, J. Berezovsky, and P. A. Crowell, Phys. Rev. Lett. 89, 277201 (2002).]

Color intensity map of the spin-wave spectrum measured along a cross-section of a ferromagnetic wire in an applied field of 150 Oe. The circles indicate the two spatially localized modes spin-wave modes that are confined at the edges of the wire.