Low-temperature transport measurements of superconductors and semiconductors in magnetic fields to 800 T

Recent innovations in sample lithography and measurement techniques have made possible electrical transport measurements on both high-T-c superconductor and semiconductor samples in the harsh environment of implosively generated magnetic fields B up to 800 T, with reliable data obtained up to 300 T. Thin films of the cuprate superconductor YBa2Cu3O7-delta have been studied with B directed parallel to the CuO planes (J parallel to B perpendicular to c-axis). At an ambient temperature of 1.6 K and a probe frequency of 0.9 GHz we find an onset of dissipation at B-on = (150 +/- 20) T, the highest field yet reported. In addition, the measured upper critical held B-c2 = (240 +/- 30) T is significantly above the paramagnetic limit for this material. Measurements on AlxGa1-xAs/GaAs parabolic quantum well structures, designed to probe the existence of a magnetically induced triplet superconducting phase, and on HgSe:Fe samples are also discussed. (C) 1998 Elsevier Science B.V. All rights reserved.