Berlin 2005 – scientific programme
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MA: Magnetismus
MA 23: Spinabh
ängiger Transport III
MA 23.7: Talk
Tuesday, March 8, 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−xOx 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 HfOx phase.
Supported by DFG-project, SA 337/9-1