The rounding of resistivity near and above the superconductivity transition temperature $T_c$, observed in the ${\mathrm{Y}}_1$ ${\mathrm{Ba}}_2$ ${\mathrm{Cu}}_3$ ${\mathrm{O}}_{9\mathrm{-}\mathrm{\delta }}$ superconductor, is found to be a manifestation of thermodynamic fluctuations. A quantitative agreement between the experiment and the three-dimensional (3D) Aslamazov-Larkin theory was achieved near $T_c$ Low-field measurements of the excess diamagnetism are also in agreement with the 3D theory of Prange. These results strongly suggest that superconductivity in high-$T_c$ copper oxides (${\mathrm{Y}}_1$ ${\mathrm{Ba}}_2$ ${\mathrm{Cu}}_3$ ${\mathrm{O}}_{9\mathrm{-}\mathrm{\delta }}$) is basically 3D in nature.

We study the magnetization damping in ion-beam deposited ${\mathrm{Co}}_{72}{\mathrm{Fe}}_{18}{\mathrm{B}}_{10}$ thin films as a function of film thickness and crystalline state. As-deposited amorphous layers showed low damping $({\alpha }_{\mathrm{app}}=0.006)$ that is thickness independent. $40\mathrm{nm}$ ${\mathrm{Co}}_{80}{\mathrm{Fe}}_{20}$ with no boron content exhibited a value twice higher $({\alpha }_{\mathrm{app}}=0.013)$ . Crystallization in ${\mathrm{Co}}_{72}{\mathrm{Fe}}_{18}{\mathrm{B}}_{10}$ , triggered by annealing at $280°\mathrm{C}$ , results in increased magnetization as well as a strong increase in damping, by a factor of 5 for $40\mathrm{nm}$ films. For lower thicknesses the damping increase upon annealing is less pronounced. The exchange stiffness constant for amorphous films is deduced from perpendicular standing spin waves to be $28.4\times {10}^{-12}\mathrm{J}∕\mathrm{m}$ . The annealing dependence of damping should have consequences for the spin-transfer switching in $\mathrm{Co}\mathrm{Fe}\mathrm{B}∕\mathrm{Mg}\mathrm{O}∕\mathrm{Co}\mathrm{Fe}\mathrm{B}$ magnetic tunnel junctions.

Magnetic bead sensors based on the planar Hall effect in thin films of exchange-biased permalloy have been fabricated and characterized. Typical sensitivities are $\text{3\hspace{0.5em}μ}\mathrm{V/Oe} \mathrm{mA}.$ The sensor response to an applied magnetic field has been measured without and with coatings of commercially available 2 μm and 250 nm magnetic beads used for bioapplications (Micromer-M and Nanomag-D, Micromod, Germany). Detection of both types of beads and single bead detection of 2 μm beads is demonstrated, i.e., the technique is feasible for magnetic biosensors. Single 2 μm beads yield 300 nV signals at 10 mA and 15 Oe applied field.