Berlin 2015 – scientific programme
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MA: Fachverband Magnetismus
MA 33: Multiferroics II (DF with DS/KR/MA/TT)
MA 33.5: Talk
Wednesday, March 18, 2015, 16:15–16:30, EB 107
Inverse TMR effect in multiferroic tunnel junctions studied from first principles — •Vladislav Borisov1,2, Sergey Ostanin2, and Ingrid Mertig1,2 — 1Institute of Physics, Martin Luther University Halle-Wittenberg — 2Max Planck Institute of Microstructure Physics
The spin-polarized electronic transport in multiferroic tunnel junctions (MTJ): Co/PTO/Co and LSMO/PTO/Co was computed from first principles. We confirm that the so-called four-state tunnelling magnetoresistance (TMR) may be detected for each MTJ when its TMR and TER are controlled by the reversible barrier polarization as well as reversible magnetization of the leads. The ab initio based results are directly compared to the experimental features of the inverse TMR recently reported for LSMO/PZT/Co [1]. We show how the observed effect originates from the magnetoelectric coupling seen at both interfaces of the MTJ [2]. The role of half-metallic LSMO as well as the effect of Zr substitutes in PTO are analysed in the context of the inversion of the TMR signal [1]. Another important issue of TMR discussed here concerns the functional (insulating) barrier thickness, which is always less than the nominal thickness and which depends on the polarization direction. We found that the functional barrier thickness is systematically reduced when the polarization is directed toward the Co electrode due to charge transfer at the Co/PTO interface.
[1] D. Pantel et al., Nat. Mater. 11, 289 (2012).
[2] V. S. Borisov et al., Phys. Rev. B 89, 054436 (2014).