Temperature-dependent study of ion-channeling in [formula omitted] superlattices

Abstract

Giant- Magneto- Resistance (GMR), as large as 150% at 4 K, occurs in Fe Cr superlattices as a result of antiferromagnetic interlayer coupling. We have successfully grown epitaxial single-crystal Fe Cr multilayers using magnetron sputtering. Ion channeling was employed to study the structural and vibrational properties of the sputter-deposited Fe Cr superlattices, and of a Cr thin film, between temperatures of 100 and 330 K. Channeling in the latter specimen was used to investigate the importance of depositing a Cr-buffer layer in order to obtain superlattices with large GMR values. Once the buffer layer exceeded a critical thickness, a high quality Cr film was observed. The epitaxial quality of the superlattices grown on such buffer layers by sputtering was found to be excellent. Minimum yields nearly equal to theoretical predictions were found for channeling along the 〈001〉 growth direction; slightly higher values were found along the 〈111〉 axis. Because of the high structural quality of the sputter-deposited films, it was possible to investigate changes in thermal vibration amplitudes, even though their magnitude is only of the order of a few pm (10 −12 m). No unusual structural changes of this magnitude were observed in angular channeling scans obtained while cooling the Fe Cr superlattice from 330 down to 100 K.