Controlling the Nonlinear Relaxation of Quantized Propagating Magnons in Nanodevices.

Relaxation of linear magnetization dynamics is well described by the viscous Gilbert damping processes. However, for strong excitations, nonlinear damping processes such as the decay via magnon-magnon interactions emerge and trigger additional relaxation channels. Here, we use space- and time-resolved microfocused Brillouin light scattering spectroscopy and micromagnetic simulations to investigate the nonlinear relaxation of strongly driven propagating spin waves in yttrium iron garnet nanoconduits. We show that the nonlinear magnon relaxation in this highly quantized system possesses intermodal features, i.e., magnons scatter to higher-order quantized modes through a cascade of scattering events. We further show how to control such intermodal dissipation processes by quantization of the magnon band in single-mode devices, where this phenomenon approaches its fundamental limit. Our study extends the knowledge about nonlinear propagating spin waves in nanostructures which is essential for the construction of advanced spin-wave elements as well as the realization of Bose-Einstein condensates in scaled systems.

Spin Pinning and Spin-Wave Dispersion in Nanoscopic Ferromagnetic Waveguides.

Spin waves are investigated in yttrium iron garnet waveguides with a thickness of 39 nm and widths ranging down to 50 nm, i.e., with an aspect ratio thickness over width approaching unity, using Brillouin light scattering spectroscopy. The experimental results are verified by a semianalytical theory and micromagnetic simulations. A critical width is found, below which the exchange interaction suppresses the dipolar pinning phenomenon. This changes the quantization criterion for the spin-wave eigenmodes and results in a pronounced modification of the spin-wave characteristics. The presented semianalytical theory allows for the calculation of spin-wave mode profiles and dispersion relations in nanostructures.

Detection of thyroid disorders by use of basal thyrotropin values determined with an optimized "sandwich" enzyme immunoassay.

To measure the concentrations of thyrotropin (thyroid-stimulating hormone), we used the components of a commercially available two-step "sandwich" enzyme immunoassay (Enzymun-Test TSH, Boehringer Mannheim) based on the specific binding of the beta-subunit of thyrotropin by monoclonal antibodies coated on polystyrene tubes. By modifying the original assay protocol, we lowered the limit of detection to 0.18 milli-int. units/L, using a total incubation period of 22 h. With this modification we could differentiate between patients responsive to administration of thyroliberin (thyrotropin-releasing factor) and those who were non-responders, by measuring only the basal concentration of thyrotropin. Furthermore, we demonstrated a correlation between the basal concentration of thyrotropin and its increase after administration of thyroliberin (r = 0.77, n = 48).