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MA: Fachverband Magnetismus

MA 3: Magnetic Half Metals and Oxides

MA 3.5: Vortrag

Montag, 23. März 2009, 12:00–12:15, HSZ 401

Photolitchemically deposited amorphous iron(III) oxide exhibiting room-temperature ferromagnetism — •Simon Trudel^1,2 and Ross H. Hill¹ — ¹4D LABS and Department of Chemistry, Burnaby, BC, Canada — ²Now at FB Physik and Forschungszentrum OPTIMAS, TU Kaiserslautern, 67663 Kaiserslautern, Germany

There is great interest in the study of new materials that exhibit useful ferromagnetic properties, while they are expected to be non-magnetic. A surprising example is amorphous iron oxide (a-Fe₂O₃), for which room temperature ferromagnetism (FM) has never been reported.

Thin films of a-Fe₂O₃ were prepared using a photochemical deposition method that allows direct patterning, without the use of photoresists. This method relies on light-induced decomposition of Fe(iii) 2-ethylhexanoate, which can be spin-coated as high-quality thin films. Upon exposure to light, the precursor decomposes, yielding a-Fe₂O₃. The a-Fe₂O₃ thin films were found to exhibit FM at room temperature. Prior to this work, no magnetic amorphous iron oxide had previously been reported (J. Phys. Chem. B 111 (2007) 4003).

The FM in these films can be tuned by changing the preparation conditions, and complete deactivation of the FM can be achieved by changing the deposition temperature. The oxidation state and coordination of the Fe centers in a-Fe₂O₃ were detemined using X-ray absorption spectroscopy. It will be shown this route to amorphous magnetic oxide materials is general, and that a-Cr₂O₃ and a-CoFe₂O₄ also exhibit unprecedented room-temperature FM.