Structural and magnetic properties of diode radio-frequency sputtered Cr/Co multilayers

Abstract

Structural properties of diode radio-frequency (rf)-sputtered Cr/Co multilayers have been investigated using in situ kinetic ellipsometry, grazing x-ray reflection, x-ray diffraction, and nuclear magnetic resonance. Results have been correlated with magnetic characterizations obtained by SQUID susceptometry. Interdiffusion along ≂10 Å occurs at the ‘‘Cr on Co’’ interface. The Co on Cr interface appears sharper. X-ray diffraction and nuclear magnetic resonance show that Co layers grow with bcc structure when the Co layer thickness dCo is lower than ≂15 Å. In this case, the films are strongly textured with the Cr bcc (100) direction perpendicular to the plane of the substrate. A better structural coherence is observed for the thinner layers. When dCo is thicker than ≂15 Å, a mixture of hcp and fcc Co phases appears by x-ray diffraction and nuclear magnetic resonance. The good structural quality of the films is confirmed by the occurrence of satellite peaks in the x-ray diffraction patterns. The Co magnetic moment extracted from the hysteresis loops measurements is coherent with these changes of the cobalt structure with layer thickness. In plane magnetization measurements show a antiferromagnetic coupling of the Co layers through the Cr layers.