Strong reduction of field-dependent microwave surface resistance in YBa2Cu3O7−δ with sub-micrometric BaZrO3 inclusions

摘要

We observe a strong reduction of the field induced thin film surface resistance measured at high\udmicrowave frequency (nu = 47.7 GHz) in YBa2Cu3O7−d thin films grown on SrTiO3 substrates, as a\udconsequence of the introduction of submicrometric BaZrO 3 particles. The field increase of the\udsurface resistance is smaller by a factor of ϳ3 in the film with BaZrO3 inclusions, while the\udzero-field properties are not much affected. Combining surface resistance and surface reactance\uddata, we conclude (a) that BaZrO3 inclusions determine very deep and steep pinning wells and (b)\udthat the pinning changes nature with respect to the pure film.