Volume 92, Issue 6, 15 September 2002
Index of content:
- MAGNETISM AND SUPERCONDUCTIVITY (PACS 74-76)
92(2002); http://dx.doi.org/10.1063/1.1498882View Description Hide Description
Cr(001)/CoCrPt films, used in magnetic hard disks, exhibit in-plane magnetic anisotropy when grown over a substrate patterned with shallow grooves. In this experiment, Cr/CoCrPt films are grown over substrates that have been patterned using lithographic techniques to produce well-controlled topography. The in-plane anisotropy, which is of the order of increases with the groove height and frequency. This magnetic anisotropy is a result of anisotropic in-plane crystallographic orientation and anisotropic stress. Stress-induced anisotropy accounts for up to 25% of the total in-plane anisotropy, but the major contribution to the anisotropy is a preferential Co c-axis alignment parallel to the groove direction.
92(2002); http://dx.doi.org/10.1063/1.1499203View Description Hide Description
Co/Fe multilayers with different layer thickness formed by electron beam evaporation in ultrahigh vacuum have been investigated by grazing incidence x-rayreflectivity (GIXRR) and alternating gradient force magnetometry. The interface thicknesses are lower than GIXRR uncertainty (∼1 nm), favoring a strong magnetic exchange interaction between the layers responsible for their single phase magnetic behavior. The hysteresis loops were interpreted as the result of two different magnetization processes related to the presence of an out-of-plane component of the magnetization.
92(2002); http://dx.doi.org/10.1063/1.1502914View Description Hide Description
The magnetocaloric effect of a single crystal was examined. From the measurements of isothermal magnetization and heat capacity around the Curie temperature, we have calculated the maximum isothermal magnetic entropy change as ∼7.5 J/kg K and the adiabatic temperature changes as ∼5.6 K, near room temperature for a 7 T magnetic field variation. Besides, the sharp drop of resistivity at the insulator–metal transition associated with the magnetic transition gives rise to a large temperature coefficient of resistance (TCR). For the and single crystal, the peak of TCR is ∼50%/K at 218 K and ∼10%/K at 290 K, respectively.
Long Josephson junction embedded into a planar resonator at microwave frequencies: Numerical simulation of fluxon dynamics92(2002); http://dx.doi.org/10.1063/1.1497466View Description Hide Description
We have investigated numerically a system consisting of a long Josephson junction embedded into a microstrip resonator. For such a configuration the Josephsonvortex dynamics in the junction is driven by the oscillating currents in the resonator. We have calculated the complex impedance of the junction at the resonant frequency. The Q factor of the resonator and the change of the resonant frequency of the whole system can then be easily calculated knowing the parameters of the resonator without Josephson junction. The fluxon dynamics and the complex impedance of the junction are simulated for different values of the junction length, damping, dc bias current, and dc magnetic field. This allows us to explain the behavior of the impedance of the junction and different loss mechanisms. In particular, we predict a nonmonotonic dependence of the both real and imaginary parts of the impedance on the amplitude of the oscillating current in the resonator for some range of parameters. Our results show that such a combination of active and passive superconducting elements forms a rather interesting nonlinear physical system which might be useful for development of tunable/switchable superconductingresonators and suggests an experimental technique for detecting trapped vortices in long junctions.