Elsevier

Thin Solid Films

Volume 380, Issues 1–2, 22 December 2000, Pages 211-214
Thin Solid Films

Giant magnetoresistance increase in a hard–soft spin valve structure with the growth of a semiconductor layer

https://doi.org/10.1016/S0040-6090(00)01507-8Get rights and content

Abstract

Magnetic and transport properties of a hard–soft spin valve structures have been investigated. A first series of sandwiches composed of an artificial antiferromagnetic (AAF) Co/Ru/Co sandwich decoupled from a soft Fe/Co buffer layer as follows: Fe50 Å/Co5 Å/Cu30 Å/Co30 Å/Ru5 Å/Co30 Å/Cu20 Å/Cr20 Å has been prepared. This sandwich presents a giant magnetoresistance (GMR) of 1.7% and an exchange coupling strength of approximately −1.73 erg/cm2. Afterwards, we have grown a second series of sandwiches in which the Cu/Cr capping layer has been replaced by a 15-Å thin semiconductor layer of ZnS, covered by a soft ferromagnetic layer of Co5 Å/Fe50 Å. Surprisingly, the giant magnetoresistance for the last sandwiches has been increased by a factor of 2, up to 4%. To explain this non-expected result, we have performed atomic force microscope imaging at the semiconductor layer surface. The results show that the semiconductor layer is not homogeneous and contains a non-negligible density of pin-holes, that are responsible of a direct magnetic coupling between the upper 30 Å Co layer of the AAF and the Co 5 Å/Fe 50 Å bilayer. This coupling induces a strong asymmetry between the magnetic layers of the AAF and consequently an enhancement of the GMR.

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Acknowledgements

This work was supported by ‘la région d'Alsace’ and the ‘SENSTRONIC’ Company in Saverne.

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