165 INFLUENCE OF LAYER STRUCTURE ON ANTIFERROMAGNETIC EXCHANGE COUPLING OF IRON FILMS THROUGH CHROMIUM INTERLAYERS A.P. Payne H. Kataoka, M. Farle, B.M. Clemens Department of Materials Science and Engineering, Stanford University, Stanford CA, 94305-2205 ABSTRACT The effect of layer structure perturbations on antiferromagnetic coupling in Fe-Cr-Fe trilayer systems is investigated. By varying the sputtering pressure, the layer structure of Fe-Cr-Fe trilayers is systematically altered, as indicated by changes in the low angle superlattice spectra of multilayers fabricated under identical conditions. The effect of topographic roughness is investigated by fabricating identical trilayers on Cr buffer layers of different thickness. Scanning tunneling microscopy is used to measure surface roughness. In each case the saturation field is measured as a function of Cr interlayer thickness by means of tapered Cr interlayer structures in which the thickness of the spacer varies linearly from 0 to 28 A upon a single substrate. Antiferromagnetic coupling is measured locally by means of the magneto-optic Kerr effect. Results show that although the coupling is diminished by structural perturbations, it is a remarkably robust effect which persists even in instances of poor layer structure. INTRODUCTION There is much current interest in the exchange coupling of ferromagnetic thin films through non- magnetic interlayers. In selected systems it has been found that ferromagnetic layers couple antiferromagnetically through a non-magnetic spacer of appropriate thickness [1,2,3]. It has since been discovered that the antiferromagnetic coupling (AFC) is a oscillatory function of interlayer thickness such that subsequent antiferromagnetic excursions appear at even larger interlayer thicknesses [4]. The antiparallel orientation of moments in the ferromagnetic layers is accompanied by a dramatic increase in magnetoresistance (giant magnetoresistance) [5,6], endowing the phenomenon with a practical significance for sensor applications. The Fe-Cr system is the most studied system exhibiting this effect, an it has been demonstrated in Fe-Cr films produced by a variety of processes. For purposes of comparison, the Fe-Cr system was selected in this experiment as well. The objective of this study was to examine the effect of layer structure on the phenomenon, with the expectation that this will aid in its eventual understanding. BACKGROUND It has long been known that sputtering pressure plays an important role in determining the the physical properties and morphology of sputter deposited films [7]. By a process known as thermalization, the initial energy of the sputtered atom is diminished through collisions with the sputtering gas atoms [8], and the fraction of initial energy lost increases exponentially with sputtering pressure [9]. Adatoms arriving with higher energy are more able to seek out low energy attachment locations than are the less energetic adatoms, and since the bulk structure of a vapor deposited film is determined largely by behavior at the growing interface, this has important consequences to the final structure of the film. We have found sputtering pressure to have dramatic effects on the layer structure of Fe-Cr-Fe multilayer films. Rapid degradation of ideal layer structure occurs as pressure is increased from 1 to 10 mT. This was used in the present study to examine the influence of layer structure on antiferromagnetic exchange coupling. The effects of topographic roughness were also investigated by fabricating Fe-Cr-Fe trilayers on chromium buffer layers of various thickness. Mat. Res. Soc. Symp. Proc. Vol. 231. 91992 Materials Research Society