Eur. Phys. J. B 18, 413-419 (2000)
https://doi.org/10.1007/s100510070027

Effect of the structural quality of the buffer on the magnetoresistance and the exchange coupling in sputtered Co/Cu sandwiches

¹ IPCMS-GEMME (UMR 7504 du CNRS) , ULP-ECPM, 23 rue du Loess, 67037 Strasbourg Cedex, France
² Siemens AG, ZT MF 1, Paul Gossenstrasse 100, 91052 Erlangen, Germany

Corresponding author: ^a aziz@ipcms.u-strasbg.fr

Received: 11 July 2000
Published online: 15 December 2000

Abstract

The effect of the structural quality of the buffer stack on the structural properties, giant magnetoresistance (GMR) and the quality of the antiferromagnetic coupling has been investigated for Co/Cu/Co sandwiches prepared by DC-magnetron sputtering. Three kinds of buffers were employed: type A: Cr(6 nm)/Co(0.8 nm)/Cu(10 nm), type B: Fe(6 nm)/Co(0.8 nm)/Cu(10 nm) and type C: Cr(4 nm)/Fe(3 nm)/Co(0.8 nm)/Cu(10 nm). For B and C type buffers, the antiferromagnetic alignment is very interesting at zero field with a coupling strength larger than 0.4 erg/cm² and a GMR signal reaching 5% at room temperature. However, for the A type buffer the antiferromagnetic coupling completely disappears, while the GMR drops to about 0.8% . X-ray diffraction, atomic force microscopy and transmission electron microscopy have been performed in order to understand the origin of the observed difference in the magnetic properties. The results show a strong difference in the average surface roughness, 1.15 nm and 0.35 nm, respectively for the A and C types buffers, and demonstrate that the quality of the surface of the buffer is the key to optimize both the GMR and the indirect exchange coupling.