Berlin 2005 – wissenschaftliches Programm

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MA: Magnetismus

MA 23: Spinabh
ängiger Transport III

MA 23.7: Vortrag

Dienstag, 8. März 2005, 12:00–12:15, TU H1028

Magnetoresistance in CoFeHfO oxide films — •Yuansu Luo, Markus Esseling und Konrad Samwer — I. Physikalisches Institut, Universität Göttingen, Friedrich- Hund Platz 1, 37077 Göttingen

Oxide films [Co₅₅Fe₂₅Hf₂₀]_1−xO_x were prepared by reactive sputtering and characterized by XRD, magnetic and electrical measurements, including XPS analysis to determine the oxygen amount x. For x < 0.1, the films are homogeneous and amorphous, showing excellent soft magnetic properties. These films were used as magnetic electrode layers in magnetotunneling junctions to simplify the oxidation process for the barrier fabrication. For large x, a chemical phase separation occurs. The films consist of two interconnected amorphous phases with dominated atomic correlation Hf-O and Co-Co(Fe) and become paramagnetic-like and insulating at low temperatures. A large magnetoresistance (MR) effect which increases with x has been observed in these films. For x=0.4, the MR value is 12 % at RT and 22 % at 10 K (7 T). The effect is similar to that observed in granular systems and related to spin dependent scattering. The large MR effect at low temperatures could be attributed to spin dependent tunneling effect across the HfO_x phase.

Supported by DFG-project, SA 337/9-1