In recent years there has been a high degree of interest in multilayer film (MLF) structures because of their applications as magnetoresistive sensors and as memory elements in magnetoresistive random access memory arrays. As each of the layers in a spin-valve-based MLF structure1 is only a few nanometers in thickness, the morphology of the layers is crucial in controlling the magnetic and transport properties of the devices. In general, the microstructural features that can influence the film properties include layer roughness, layer composition, interfacial chemical mixing, grain size, grain boundary morphology, and crystallographic orientation, with the most important microstructural parameter being the nature of the interfaces between adjacent layers. With so many internal interfaces, each of which can have a different morphology and degree of intermixing, it is extremely difficult to determine the nature of each individual interface unless a technique is used that can analyze them independently, and with high spatial resolution.