59Co nuclear magnetic resonance was used to study the bulk and interface microstructure in the unpinned Co layer in a series of highly (111)-textured ion beam deposited spin valves. The intent of the study is to determine the degree of Co interface intermixing and any possible variation of the Co layer microstructure as a result of weakening (111) texture of the NiFe/Co/Cu/Co/NiFe/FeMn film stack. We found that the interfaces are diffused over ∼2 monolayers on both sides of the Co layer, involving an equivalent of about 3 Å of Co per interface and vary only slightly with deteriorating texture. The main structural change is the drop of perfect fcc stacking in the Co layer. © 1999 American Institute of Physics.