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Tailoring TMR Ratios by Ultrathin Magnetic Interlayers: A First-principles Investigation of Fe/MgO/Fe

Published online by Cambridge University Press:  31 January 2011

Peter Bose ,
Peter Zahn ,
Juergen Henk  and
Ingrid Mertig
Peter Bose
Affiliation:
peter.bose@physik.uni-halle.de, Physics Institute of the Martin Luther University Halle-Wittenberg, Theory Department, von Seckendorff-Platz 1, Halle (Saale), D-06120, Germany, +493455525460
Peter Zahn
Affiliation:
peter.zahn@physik.uni-halle.de, Physics Institute of the Martin Luther University Halle-Wittenberg, Theory Department, Halle (Saale), Germany
Juergen Henk
Affiliation:
henk@mpi-halle.mpg.de, Max Planck Institute of Microstructure Physics, Theory Department, Halle (Saale), Germany
Ingrid Mertig
Affiliation:
ingrid.mertig@physik.uni-halle.de, Physics Institute of the Martin Luther University Halle-Wittenberg, Theory Department, Halle (Saale), Germany
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Abstract

For spintronic device applications, large and in particular tunable tunnel magnetoresistance (TMR) ratios are inevitable. Fully crystalline and epitaxially grown Fe/MgO/Fe magnetic tunnel junctions (MTJs) are well suited for this purpose and, thus, are being intensively studied [1]. However, due to imperfect interfaces it is difficult to obtain sufficiently large TMR ratios that fulfill industrial demands (e.g. [2]).

A new means to increase TMR ratios is the insertion of ultra-thin metallic buffer layers at one or at both of the Fe/MgO interfaces. With regard to their magnetic and electronic properties as well as their small lattice mismatch to Fe(001), Co and Cr spacer are being preferably investigated.

We report on a systematic first-principles study of the effect of Co and Cr buffers (with thicknesses up to 6 ML) in Fe/MgO/Fe magnetic tunnel junctions (MTJs) on the spin-dependent conductance. The results of the transport calculations reveal options to specifically tune the TMR ratio. Symmetric junctions, i.e. with Co buffers at both interfaces, exhibit for some thicknesses much larger TMR ratios in comparison to those obtained for Fe-only electrodes. Further, antiferromagnetic Cr films at a single interface introduce TMR oscillations with a period of 2 ML, a feature which provides another degree of freedom in device applications. The comparison of our results with experimental findings shows agreement and highlights the importance of interfaces for the TMR effect.

Keywords

spintronicmagnetoresistance (transport)magnetoresistance (magnetic)
Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 1183: Symposium FF – Novel Materials and Devices for Spintronics , 2009 , 1183-FF07-02
Copyright
Copyright © Materials Research Society 2009

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References

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