Nuclear magnetic resonance of molecular beam epitaxially grown Co-Cu superlattices that exhibit large magnetoresistance

The 59Co NMR has been measured for superlattices of Co(15 Å)/Cu (7 or 18 Å) grown with either a Au or Cu buffer layer between the substrate and the superlattice. As was reported earlier the Co (15 Å)/Cu (7 Å) (Au) superlattice has the largest magnetoresistance (ΔR/R∼26%) known for a MBE grown Co/Cu multilayer. The NMR measurements show that the Au-based superlattices have very flat interfaces and (111) orientation, two features which were supposed to preclude a large value of ΔR/R, and that the average strain in the Co layers is greater for a Au than a Cu buffer layer.