Electron mass anisotropy of BaZrO3 doped YBCO thin films in pulsed magnetic fields up to 30 T

The high anisotropy of the critical current density in the high-temperature superconductor YBa2Cu3O6+x can be compensated by changing the pinning landscape, for example, through doping with BaZrO3. We measure the change due to BaZrO3 doping in the effective electron mass anisotropy, γ, by resistive measurements of the upper critical field in pulsed high magnetic fields. It is found that the angular dependence of the upper critical field follows the Blatter scaling up to 30 T but the irreversibility field does not. We also report a significant reduction in the effective electron mass anisotropy from 6.0 to 3.4 by BaZrO3 doping. (paper)