Experimental evidence of the spin-dependence of electrons reflections in magnetic multilayers

Bertrand Raquet 3Etienne Snoeck 1Christophe Gatel 1Raphael Serra 1Jean-Claude Ousset 1Jean-Baptiste Moussy 2Alexandre Bataille 2M. Pannetier 2M. Gautier-Soyer 2Jean Marc Broto 3

1. CEMES-CNRS (CEMES-CNRS), 29, rue Jeanne Marvig, Toulouse F31055, France
2. CEA-Saclay, Bat 522, Gif-sur-Yvette 91191, France
3. Laboratoire National des Champs Magnétiques Pulsés, av. de Rangueil, Toulouse 31423, France

Abstract

The giant magnetoresistance (GMR) of multilayers in the current in plane (CIP) geometry can be understood by considering the spin-dependent scattering effects within the magnetic layers and at the non magnetic/magnetic interfaces. In this paper we experimentally put on view the magnetoresistance effect created only by the spin-dependent reflection of electrons at the interfaces. Two epitaxial systems were studied, consisting of two ferrimagnetic insulators layers at low temperature (CoFe2O4 and Fe3O4) separated by a non magnetic metallic layer (M= Au or Pt). The transport properties indicate that conduction of the CoFe2O4/M/Fe3O4 trilayers take place within the thin metallic layer. An optimal magnetoresistance up to 5 % at 10 K associated to the switching from parallel to anti-parallel configuration of the magnetization of the two ferrite layers has been obtained. It is associated to the spin-dependent interfacial scattering contribution of the CIP-GMR.
An augmentation of the GMR is observed when decreasing the metallic layer thickness or increasing the oxide layers width suggesting this GMR is essentially an interfacial phenomenon. Moreover, ion implantation experiments were performed on such trilayers: at low doses (N+ ions at 150 keV for doses <1013 ion/cm2) improves the GMR properties of the Au-based trilayers while for higher doses the magnetoresistance drastically vanishes. In such low dose ranges the damages induced in the MLs is very low (~ 5. 10-2 eV/at) and mostly located at interfaces. Our experiments suggest that the effect of low doses ion implantation is a slight smoothing of the interfaces which confirms the interfacial nature of the GMR.
The Pt-based system shows an additional AMR which is not evidenced in the Au-based trilayer. We suggest that this AMR comes from the polarization of the Pt layer by the ferrimagnetic oxides.

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Presentation: poster at E-MRS Fall Meeting 2005, Symposium D, by Bertrand Raquet
See On-line Journal of E-MRS Fall Meeting 2005

Submitted: 2005-05-30 15:56
Revised:   2009-06-07 00:44
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