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MA: Fachverband Magnetismus

MA 15: Poster:ThinFilms(1-33),Transp.(34-49),ExchBias(50-56),
Spindynamics(57-70),Micro-nanostr.Mat.(71-82),
Particles/Clust.(83-88), Mag.Imag./Surface(89-96),
Spinelectronics(97-109), Theory/Micromag.(110-116),
Spinstruct/Phasetr.(117-128),Magn.Mat.(129-139),
Aniso.+Measuring(140-145), MolMag.(146-152),
MSMA(153-156)

MA 15.49: Poster

Dienstag, 27. März 2007, 15:00–19:00, Poster A

Comparison between MgO and AlO_x barriers in Co₂Cr_0.6Fe_0.4Al-Tunnel Junctions — •Christian Herbort, Andres Conca, Martin Jourdan, and Hermann Adrian — Institut für Physik, Johannes Gutenberg Universität, Staudinger Weg 7, 55128 Mainz, Germany

In magnetic tunnel junctions with conventional ferromagnetic electrodes MgO proved to be a superior barrier material concerning the achievable tunnel magnetoresistance effect (TMR). Alternatively, large TMR effects could be obtained by employing novel materials with high spin polarisation. On example for such a material is the Heusler compound Co₂Cr_0.6Fe_0.4Al (CCFA). We compare the TMR effect of CCFA based tunnel junctions with amorphous AlOx and epitaxial MgO barriers. Whereas we have already optimized junctions with AlO_x barriers and obtained TMR effects which can be associated to a spin polarization of the CCFA > 50 %, the process of MgO deposition requires further improvement. The interface at the barriers is characterized by in situ RHEED and LEED as well as by STM investigations. It is shown that epitaxial MgO can be grown by rf-magnetron sputtering on epitaxial (100) oriented CCFA thin films. The barrier morphology of AlO_x and MgO is compared by transmission electron microscopy (TEM) and related to the TMR effect. The dependence of the TMR effect on the major preparation parameters is shown.