Regensburg 2007 – wissenschaftliches Programm

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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 15.42: Poster

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

Structural properties and transport behaviour of polycrystalline Co₂Cr_0.6Fe_0.4Al films as electrode materials in MTJs — •Rainer Kaltofen¹, Hartmut Vinzelberg¹, Dieter Elefant¹, Ingolf Mönch¹, Joachim Schumann¹, and Rainer Grötzschel² — ¹IFW Dresden, P.O.Box 27 01 16, D 01171 Dresden — ²Institute of Ion Beam Physics and Materials Research, FZ Dresden-Rossendorf, P.O. Box 51 01 19, D 01314 Dresden, Germany

Owing to the high spin polarization predicted for ferromagnetic half-metallic Heusler alloys many experimental attempts are known to verify this feature on real systems. The present work studies polycrystalline Co₂Cr_0.6Fe_0.4Al (CCFA) films prepared by dc magnetron sputtering. The film composition checked by RBS and PIXE is in good correspondence with the target composition. X-ray studies showed a disordered B2 structure characterized by Co-Al antisite defects. Saturation magnetization measurements by SQUID magnetometry at T=4K showed the number of Bohr magnetons per formula unit to vary between N_B/FU=2...3 in dependence on the deposition substrate temperature and annealing treatments. A strong influence of these treatments on the magnetization temperature dependence is observed. The TMR results exhibit a marginal influence of preparation conditions (T_S,p_Ar,T_ann), however the best values did not exceed ∼ 30% at 4.2 K indicating that half-metallic behaviour of the CCFA films is not observed. The main reason of the failure of high spin polarization predicted for CCFA seems to be the imperfect crystalline structure suppressing the formation of a half-metallic band structure.