2 research outputs found
Upper Critical Fields and Critical Current Densities of Fe-based Superconductors as Compared to Those of Other Technical Superconductors
Three years since the discovery by the Hosono\u2019s group of Fe-based superconductors, an enormous
number of compounds, belonging to several different families have been discovered and fundamental properties
have been deeply investigated in order to clarify the interplay between magnetisms and superconductivity in
these compounds. Indeed, the actual potential of these compounds for practical applications remains still
unclear.
Fe-based superconductors are midway between high temperature superconductors (HTSC) and MgB2. In Febased
superconductors the critical current is rather independent of the field, similarly to HTSCs, as a
consequence of the exceptionally high upper critical field and strong pinning associated with nm-scale local
modulations of the order parameter. They exhibit low anisotropy of the critical current with respect to the
crystalline directions, as in the case of MgB2, which allows current flow along the c-axis. However, Fe-based
superconductor polycrystalline materials currently available still exhibit electromagnetic granularity, like the
HTSCs, which suppresses superconducting current flow over long length. Whether the nature of such
granularity is extrinsic, as due to spurious phases or cracks between grains or intrinsic, as related to
misalignment of adjacent grains, is under debate. These aspects will be review in the light of the recent literature
Superconducting Properties of V3Si Thin Films Grown by Pulsed Laser Ablation
We present a systematic study of the superconducting properties of high quality V3Si thin films, grown by high vacuum pulsed laser deposition from a stoichiometric target, a technique never reported in literature for this compound. By changing both the substrate (crystal structure and orientation) and the deposition conditions (substrate temperature, target-substrate distance, laser frequency and pulse energy) the critical temperature and the resistivity values of the samples have been finely tuned. Best results (T-C = 16.1 K and Residual Resistivity Ratio RRR = 8.5) are obtained for deposition temperatures higher than 1200 degrees C on both LaAlO3 and MgO substrates. All the samples are polycrystalline, that however does not affect the good quality of the transport properties. The possibility of multiband superconductivity in this compound is investigated, probing as a function of temperature: (i) the critical field up to 28 T using voltamperometric measurements, and (ii) the superfluid density via magnetic penetration depth measurements with a single coil inductive technique operating in the MHz region