Magnetoresistance and Upper Critical Fields of Oriented TlBaCaCuO Thin Films in Pulsed High Magnetic Fields up to 40 T

Abstract

The magnetoresistance was measured on oriented thin film TlBaCaCuO samples in pulsed high magnetic fields up to 40 T, by a PSD method at frequencies of 200 kHz, for the two fundamental orientations of the film in the magnetic field. T_c was defined at the midpoint of the transition curve. We obtained −dB_c2^⁄⁄⁄dT=20 T/K and −dB_c2^⊥⁄dT=0.6 T/K, for the magnetic field parallel and perpendicular to the film plane, respectively, which give a large anisotropy of the upper critical field B_c2(T) of 33. The estimated coherence lengths are ξ_⊥(0)=0.8 Å and ξ_⁄⁄(0)=28 Å.