Localized spin-wave modes and microwave absorption in random-anisotropy ferromagnets

Crosstalk of propagating and localized spin-wave modes

The relaxation mechanisms in thin nickel films are investigated with all optical pump-probe experiments. Magnetic oscillations in the GHz range can be attributed to the uniform precession (Kittel mode) and spin waves with dipole character (Damon-Eshbach surface modes). Applying an external field changes both oscillation amplitude and frequency yielding experimental dispersions ν(Hext). On a wed...

Magnetic behavior of ferromagnets with random anisotropy

This article reports on a magnetometric study of the effects of diluted local random anisotropy in a ferromagnetic FegoB20 amorphous matrix. In the low-temperature and low-field regime the samples, Fe74RE6B20 (RE = Nd, Ce), show a very rich behavior as a consequence of the competition between, and different dependence on T, of the correlation length associated with local random anisotropy and e...

Localized modes in random arrays of cylinders.

Anderson localization of classical waves in random arrays of dielectric cylinders is numerically investigated as a function of the distribution of their diameters. We show that using polydispersed resonant scatterers increases the localization length, while using identical resonant scatterers fosters Anderson localization. We discuss this collective process and link it to the effect of proximit...

Spin-wave modes in magnetic nanowires

Spatially resolved dynamics of localized spin-wave modes in ferromagnetic wires.

We have observed localized spin-wave modes in individual thin-film ferromagnetic wires using time-resolved Kerr microscopy as a micron-scale spectroscopic probe. The localization is due to the internal field profile present when an external field is applied in the plane of the film and perpendicular to the long axis of the wire. Spatially resolved spectra demonstrate the existence of distinct m...