Magneto transport study of YBCO: Ag composites

• The addition of Ag in YBCO makes the transition sharp without changing TC.
• In presence of magnetic field, the zero resistance transition temperature shifts less in YBCO+Ag compared to pure YBCO.
• This makes the composite interesting material for magnetic environment.
• Addition of Ag in YBCO increases the activation energy of flux lines vital for YBCO to sustain large magnetic field and JC.
• Vortex glass transition temperature is found to increase with the addition of Ag.
• This means addition of Ag helps to cease the thermally activated motion of vortices.
• Two independent methods show a significant enhancement of zero temperature HC2 by the addition of Ag in YBCO.

We study the effect of Ag addition on the magnetoresistance and allied properties of YBCO. We find that the zero resistance temperature (TC0) shift is narrowed down by the addition of Ag as magnetic field (H) is increased from 0 to 13 T. The resistivity broadening of composites under magnetic field exhibits Arrhenius behavior due to thermally activated flux flow of vortices. The activation energy, determined from Arrhenius plot of resistivity, increases with the addition of Ag in YBCO and is found optimum for 15%Ag composite. The vortex glass transition temperature is found more in YBCO:Ag composites as compared to pristine YBCO. The zero temperature upper critical field Hc2(0) estimated by using Werthamer, Helfand and Hohenberg theory and Ginzburg Landau theory shows two fold enhancement by adding Ag in YBCO matrix. We find that the addition of Ag in YBCO leads to an enhancement in activation energy, an increases in Hc2(0) in addition to better grain connectivity.