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Abstract:
Scanning Hall probe microscopy has been used to search for spontaneous
fields at the well-defined edges of large mesoscopic disks, etched into
the ab surface of very high quality single crystal Sr2RuO4. Such fields
are predicted to exist at locations of broken translational symmetry as
a consequence of the proposed two-component spin-triplet chiral order
parameter (d) over cap = Delta(0)(k(x) +/- ik(y))(z) over cap. We find
no evidence for such fields and impose an upper limit of +/-2.5 mG on
their magnitude. We do, however, observe an abrupt apparent loss of
strong bulk pinning and a change in the screening behavior above H
similar to 25 Oe. At high fields (H > 25 Oe) pronounced magnetic
screening by the disks is very well described by a model containing only
strong edge currents, and bulk critical currents do not appear to play a
significant role. Our results are discussed in terms of relevant
theoretical predictions.
