Scanning SQUID imaging of Sr$_{2}$RuO$_{4}$ and PrOs$_{4}$Sb$_{12}$

We present scanning SQUID magnetometer data on the superconducting materials strontium ruthenate (Sr$_{2}$RuO$_{4})$ and praseodymium-osmium-antimonide (PrOs$_{4}$Sb$_{12})$, both of which are believed to have spin-triplet pairing and to generate spontaneous time-reversal-symmetry-breaking fields below their superconducting transition temperatures. Our images, taken with a SQUID with a resolution of 3$\mu $m and approximately 100$\mu $G, do not show evidence for spontaneous TRSB fields, in contrast with muon spin rotation data which indicates gauss-scale fields in both materials. The fields indicated by $\mu $SR data must therefore have a short length scale and/or a short time scale. Supposing that the TRSB fields are static with the magnitudes indicated by $\mu $SR data we place upper limits on their length scales in both Sr$_{2}$RuO$_{4}$ and PrOs$_{4}$Sb$_{12}$. We also place upper limits on the strength of any distributed fields that might exist at sample edges and order parameter domain walls.