Effective penetration depth in the vortex state of a D-wave superconductor

temperature and the field dependence of the effective magnetic penetration depth (lambda(eff)) in the vortex state of a d-wave superconductor, as measured by muon spin rotation (mu SR) experiments, is calculated using a nonlocal London model. We show that at temperatures below T* proportional to root B, the linear T dependence of lambda(eff)(-2) crosses over to a T-3 dependence. This could provide an explanation for the low temperature flattening of the lambda(eff)(-2) curve observed in a recent mu SR experiment.