Magnetic instabilities along the superconducting phase boundary of Nb/Ni multilayers

We report vibrating reed and superconducting quantum interference device magnetometer data that exhibit prominent dips or oscillations of the superconducting (SC) onset temperature, Delta T(C)(H)approximate to 0.01-0.7 K, for a [Nb(23 nm)/Ni(5 nm)](5) multilayer (ML) in dc magnetic fields applied nearly parallel to the ML plane. The vibrating reed data exhibit reproducible structures below T(C) that may reflect multiple SC transitions, but they are sensitive to ac field amplitude and dc field orientation. This striking behavior poses challenges for theoretical and experimental investigations of interfaces between SC and ferromagnetic layers that involve magnetic pair breaking effects, "pi phase shifts" of the SC order parameter, and exotic ("LOFF") pairing states. Alternatively, the anomalies may mark dynamical instabilities within a confined, strongly anisotropic Abrikosov vortex lattice

Programa Nacional de Cartas Geológicas de la República Argentina

Fil: Baumann, Valérie. Servicio Geológico Minero Argentino. Instituto de Geología y Recursos Minerales. Dirección de Geología Ambiental y Aplicada; Argentina.Fil: Villegas, Daniela. Servicio Geológico Minero Argentino. Instituto de Geología y Recursos Minerales. Dirección de Geología Ambiental y Aplicada; Argentina.Fil: Seggiaro, Raúl. Servicio Geológico Minero Argentino. Delegación Salta; Argentina.Fil: Azcurra, Diego. Servicio Geológico Minero Argentino. Instituto de Geología y Recursos Minerales. Unidad de Sensores Remotos y SIG; Argentina.Fil: Tobío, María Inés. Servicio Geológico Minero Argentino. Instituto de Geología y Recursos Minerales. Dirección de Geología Ambiental y Aplicada; Argentina.Fil: Benitez, Javier. Servicio Geológico Minero Argentino. Instituto de Geología y Recursos Minerales. Unidad de Sensores Remotos y SIG; Argentina

Joule heating and high frequency nonlinear effects in the surface impedance of high Tc superconductors

Using the dielectric resonator method, we have investigated nonlinearities in the surface impedance Zs = Rs + jXs of YBa2Cu3O7 thin films at 10 GHz as function of the incident microwave power level and temperature. The use of a rutile dielectric resonator allows us to measure the precise temperature of the films. We conclusively show that the usually observed increase of the surface resistance of YBa2Cu3O7 thin film as function of microwave power is due to local heating