Berlin 2005 – scientific programme

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MA: Magnetismus

MA 20: Poster:Schichten(1-29),Spintrsp(30-45),Ex-Bias(46-63),Spindyn(64-75),Mikromat.(76-80),Cluster(81-94),Abbv.(95-99),Obflm(100-02),SpElek.(103-09),E-Theo(110-14),Mikromag.(115-16),Spin+PÜ(117-26),Mag.Mat.(127-51),Meth.(152-55),Mol.Mag(156-59),Kondo(160-65

MA 20.37: Poster

Monday, March 7, 2005, 14:00–18:00, Poster TU C

Large room temperature TMR effect in Fe₃O₄ based magnetic tunnel junctions — •Edwin Menzel, Suleman Qureshi, Daniel Reisinger, Andreas Erb, Matthias Opel, and Rudolf Gross — Walther-Meißner-Institut, Bayerische Akademie der Wissenschaften, Walther-Meißner-Str. 8, 85748 Garching

Magnetite (Fe₃O₄) is an interesting candidate for applications in spin electronics. It shows a Curie temperature of 860 K and has been predicted to be half-metallic at room temperature [1]. We have fabricated Fe₃O₄/oxide/FM (FM = Ni, Co, Fe₃O₄) trilayer structures using pulsed laser deposition and electron beam evaporation. The thin film stacks have been studied by in-situ RHEED, SQUID magnetometry, and high-resolution X-ray diffraction. Magnetic tunnel junctions have been fabricated using optical lithography and Ar ion beam milling. The junctions have been characterized by magnetotransport measurements between 150 K and 350 K. They show a reproducible tunneling magnetoresistance (TMR) effect with almost ideal switching behavior. We obtain TMR values of up to 20% for Fe₃O₄/AlO_x/Co and Fe₃O₄/AlO_x/Ni at room temperature. We also found a geometry enhanced TMR effect due to an inhomogeneous current distribution in the junction electrodes. This effect has been modeled by finite element methods. We find that the geometry enhanced TMR effect can be optimized by adjusting the junction geometry and the electrode resistivity. In our experiments, reproducible TMR effects exceeding 1000% at room temperature have been found.
This work is supported by the BMBF via grant no. 13N8279.

[1] Z. Zhang, and S. Satpathy, Phys. Rev. B, 44, 13319 (1991).