MnxPt1–x(25nm)/Co(8.0nm) antiferromagnetic/ferromagnetic (AF/F) bilayers were grown via dc magnetron sputtering at room temperature on Si(111) substrates. Samples were annealed in a vacuum in a 1200Oe magnetic field at various temperatures TA after growth. The Mn concentration x was determined from the MnPt lattice parameters and Rutherford back-scattering spectroscopy. The maximum exchange bias (HE) was observed for x~0.50, in agreement with previous work. Annealing caused the MnPt to form an ordered face-centered-tetragonal CuAu ordered structure which was necessary to observe HE. However, X-ray reflectivity indicated that an interdiffusion region exists at the MnPt/Co interface. The interdiffusion increased with TA, resulting in lower HE. The TA that maximizes HE, 318C, was a compromise between the volume fraction of MnPt forming the ordered CuAu structure, which increased HE, and the amount of interdiffusion, which decreased HE.Interdiffusion and Exchange Bias in the MnxPt1–x/Co System. E.H.Morales, Y.Wang, D.Lederman, A.J.Kellock, M.J.Carey: Journal of Applied Physics, 2003, 93[8], 4729-33