DC magnetic penetration depth of UPt3 and Sr2RuO4: implications for the superconducting order parameters

In order to distinguish the superconducting phases of the title compounds w e have studied their DC magnetic properties in low fields with a SQUID magn etometer. The magnetic penetration depth of UPt3 shows the second supercond ucting transition at T-c(-) when the field is applied along the c-axis. but not with H perpendicular toc. This result, combined with a power law behav ior of lambda at low temperatures, is most consistent with the two-dimensio nal E-2u order parameter symmetry. Below 20 mK we find an additional diamag netic signal which we ascribe to the normal state magnetism. For Sr2RuO4, s upposedly a p-wave superconductor. we find a sharp single diamagnetic trans ition at 1.08 K showing that our sample is of high quality, but there is no indication of an unusual superconducting behavior. (C) 2001 Elsevier Scien ce B.V. All rights reserved.