Dresden 2006 – scientific programme
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MA: Magnetismus
MA 30: Spin-Electronics II
MA 30.3: Talk
Thursday, March 30, 2006, 15:45–16:00, HSZ 103
Large room temperature TMR effect in tunnel junctions based on magnetite — •Andrea Boger, Edwin Menzel, Suleman Qureshi, Daniel Reisinger, Wolfgang Kaiser, Sebastian T. B. Goennenwein, Matthias Opel, and Rudolf Gross — Walther-Meissner-Institut, Bayerische Akademie der Wissenschaften, Walther-Meissner-Str. 8, 85748 Garching
To realize magnetic tunnel junctions with high tunneling
magnetoresistance (TMR) at room temperature, the ferromagnet
magnetite (Fe3O4) is attractive. The Curie temperature TC
is 860 K, and it has been predicted to be a half-metal [1].
To experimentally determine the spin polarization, we have
investigated properties of magnetic tunnel junctions (MTJs) with
Fe3O4 as the bottem electrode, fabricated by pulsed laser
deposition. Ni or Co served as counter electrodes, and AlOx as
the tunnel barrier.
The MTJs were patterned in different shapes and areas.
Measurements of magnetotransport and dc magnetization were done
between 150 K and 350 K. They show ideal switching behavior and
match to each other. TMR effects up to 20 % for
Fe3O4/AlOx/Co and 11 % for Fe3O4/AlOx/Ni could
be reached at 300 K. From this follows a spin polarization of
about 44 % for Fe3O4. In addition, the temperature and
voltage dependence of the TMR has been studied. We also observed a
large geometrically enhanced TMR of more than 1000 % at 300 K,
which is due to an inhomogeneous current distribution in the MTJs.
This work is supported by the BMBF project 13N8279.
[1] Z. Zhang, and S. Satpathy, Phys. Rev. B 44, 13319 (1991).