Complex microwave conductivity of YBa2Cu3O7 in magnetic fields up to 500 T

Abstract The complex microwave conductivity of thin, oriented YBa 2 Cu 3 O 7 films was measured at 94 GHz in pulsed, ultrahigh-magnetic fields up to 500 T. The c -axis of the film was perpendicular to the magnetic field. We estimate the upper critical field of the film at absolute zero as B c2 (0) = 340 ± 40 T. Dynamics of the transition into a normal state and connection with previous measurements of the reversibility line are discussed.