μSR studies of the superconducting order parameter in PuCoGa5

We present transverse-field (TF) measurements of the in-plane magnetic-field penetration depth),(T) in single-crystalline PuCoGa5 (T-c = 18.5 K) for 0.06 T applied field (approximate to 2 - 5 x H-cl). We find that the temperature dependence of the superfluid density, and therefore Delta lambda(T) = lambda(T) - lambda(0), is proportional to T for T/T-c <= 0.5. We estimate that the measured lambda(0) = 241(3) nm. ZF measurements find no evidence for time-reversal symmetry violation. The ZF and TF measurements are consistent with an even-parity (pseudo-spin singlet), d-wave pairing state. (c) 2005 Elsevier B.V. All rights reserved.