Influence of Cr growth on exchange coupling in Fe/Cr/Fe(100) (invited) (abstract)

Abstract

The giant magnetoresistance and the interlayer exchange coupling between magnetic layers separated by nonmagnetic spacer layers are sensitive to the roughness at the interfaces in multilayer magnetic structures. We present scanning tunneling microscopy (STM) measurements of the thickness fluctuations in Cr films grown at different temperatures on near-perfectly flat Fe(100) whiskers and correlate these results with our scanning electron microscopy with polarization analysis (SEMPA) measurements of the oscillations of the exchange coupling in Fe/Cr/Fe(100) structures grown at similar temperatures. Layer-by-layer growth was observed by STM for Cr deposition on an Fe substrate at deposition temperatures greater than 300 °C. The SEMPA measurements of the Fe overlayer magnetization as a function of Cr spacer layer thickness for Cr growth at this temperature could be simulated well by oscillatory coupling with periods 2.105±0.005d and 12±1d, where d is the layer spacing. Rougher Cr growth, limited by diffusion kinetics, is observed at lower temperatures, giving a distribution of thicknesses in the growth front. We modeled the Fe magnetization for lower temperature Cr growth by assuming that the exchange coupling at each discrete Cr thickness is the same as found for layer-by-layer growth. The total coupling at each average Cr spacer layer thickness was determined by adding the weighted contribution to the coupling from each Cr layer thickness contributing to the average thickness. Very good agreement was obtained with the SEMPA measurement of the Fe overlayer magnetization for Cr growth at lower temperatures without including other consequences of roughness at the interface, such as the breakdown of translational invariance.