MgB_(2)is a perspective superconductor for many power applications.How this potential refers also to microwave or radiofrequency applications is still to be determined.Although its ultimate surface resistance in zero ...MgB_(2)is a perspective superconductor for many power applications.How this potential refers also to microwave or radiofrequency applications is still to be determined.Although its ultimate surface resistance in zero field is not competitive with conventional metallic superconductors,its strong pinning properties can favor RF applications in a dc magnetic field.Nonetheless,the RF response in the vortex state has been relatively less studied,as well as the effect of artificial pinning centers on the microwave surface resistance in the mixed state.In this paper we study the surface resistance of spark-plasma-sintered MgB_(2),with and without Te and cubic-BN(cBN)addition,in a dc magnetic field up to 1.2 T.We summarize previous results on pure MgB_(2),and we present new data on Te-and cBN-added MgB_(2).We use a two-tone dielectric-loaded resonator to measure the field-dependent surface resistance at 16.5 and 26.7 GHz in the temperature range from 10 K to T_(c).By exploiting the simultaneous measurements at two frequencies,we extract the flux-flow resistivity,the pinning constant k_(p)and the depinning frequency f_(p).The two-band nature of MgB_(2)affects the field dependence of the flux-flow resistivity.The microscopic superconducting state is not affected by the addition of artificial pinning centers,indicating that Te and cBN do not affect interband or intraband scattering.Pinning shows a measurable trend towards an increase in the Te-and cBN-added samples at higher temperatures and fields.We finally compare the results to those obtained in bulk Nb3 Sn,also in view of possible in-field RF applications such as microwave cavity-based haloscopes.展开更多
基金supported by INFN-Commissione ScientificaNazionale 5 projects‘SAMARA’and‘SuperMAD’,COST Action CA19108-Hi-SCALE,and Italian National Operational Programme(PON)on Research and Innovation 2014-2020-Action IV.6.P.B.,A.C.M.A.G.acknowledge UEFISCDI Romania through Core Program PC2-PN23080202project POC 37697 no.28/01.09.2016 REBMAT.Data for the phase diagram of MgB_(2)and comparison to Nb3Sn was supported by Rome Technopole.
文摘MgB_(2)is a perspective superconductor for many power applications.How this potential refers also to microwave or radiofrequency applications is still to be determined.Although its ultimate surface resistance in zero field is not competitive with conventional metallic superconductors,its strong pinning properties can favor RF applications in a dc magnetic field.Nonetheless,the RF response in the vortex state has been relatively less studied,as well as the effect of artificial pinning centers on the microwave surface resistance in the mixed state.In this paper we study the surface resistance of spark-plasma-sintered MgB_(2),with and without Te and cubic-BN(cBN)addition,in a dc magnetic field up to 1.2 T.We summarize previous results on pure MgB_(2),and we present new data on Te-and cBN-added MgB_(2).We use a two-tone dielectric-loaded resonator to measure the field-dependent surface resistance at 16.5 and 26.7 GHz in the temperature range from 10 K to T_(c).By exploiting the simultaneous measurements at two frequencies,we extract the flux-flow resistivity,the pinning constant k_(p)and the depinning frequency f_(p).The two-band nature of MgB_(2)affects the field dependence of the flux-flow resistivity.The microscopic superconducting state is not affected by the addition of artificial pinning centers,indicating that Te and cBN do not affect interband or intraband scattering.Pinning shows a measurable trend towards an increase in the Te-and cBN-added samples at higher temperatures and fields.We finally compare the results to those obtained in bulk Nb3 Sn,also in view of possible in-field RF applications such as microwave cavity-based haloscopes.
