INFLUENCE OF CR GROWTH ON EXCHANGE COUPLING IN FE CR/FE(100)/

Scanning electron microscopy with polarization-analysis (SEMPA) measur ements of the dependence of the oscillations of the exchange coupling in Fe/Cr/Fe(100) structures on the Cr growth temperature are correlate d with the thickness fluctuations in Cr films measured by scanning tun neling microscopy (STM) at similar growth temperatures. Layer-by-layer growth was observed by STM for Cr deposition on very flat Fe(100) whi skers at deposition temperatures greater-than-or-equal-to 300-degrees- C. The SEMPA measurements of the magnetization of the Fe overlayer as a function of Cr spacer-layer thickness at this temperature could be s imulated well by oscillatory coupling with periods 2.105+/-0.005d and 12+/-1d, where d is the layer spacing. Rougher Cr growth, limited by d iffusion kinetics, occurs at lower growth temperatures giving a distri bution of thicknesses in the growth front as determined by STM. We mod eled the Fe magnetization for lower-temperature Cr growth by assuming that the exchange coupling at each discrete Cr thickness is the same a s found for layer-by-layer growth. The total coupling at each average Cr spacer-layer thickness was determined by adding the weighted contri bution to the coupling from each Cr layer thickness contributing to th e average thickness. Thus, by taking into account the thickness fluctu ations in the Cr spacer layer as determined by STM, very good agreemen t was obtained between the model and the SEMPA measurement of the Fe o verlayer magnetization for Cr growth at lower temperatures without inc luding other consequences of roughness at the interface, such as the b reakdown of translational invariance. Important characteristic length scales and the role of biquadratic coupling in the SEMPA measurements are addressed.