Regensburg 2010 – wissenschaftliches Programm

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MA: Fachverband Magnetismus

MA 6: Magnetic Thin Films I (Heusler Alloys)

MA 6.16: Vortrag

Montag, 22. März 2010, 18:30–18:45, H10

Kinetically controlled growth of iron oxides — •Mehrdad Baghaie Yazdi, David Bierwagen, and Lambert Alff — TU Darmstadt, Materialwissenschaft, Darmstadt, Deutschland

Magnetite is a promising material for spintronics applications due to its high Curie-temperature of 858 K, predicted half-metallicity and fairly low resistivity of 5.2 ×10⁻³ Ωcm. We have deposited magnetite thin films using reactive rf-magnetron sputtering on MgO and c-cut Al₂O₃ substrates. Furthermore the aforementioned substrate materials can also act as an insulating tunneling barrier in magnetic tunnel junction structures, making the epitaxial growth of all-oxide heterostructures possible.

The thin film samples were characterized by x-ray diffraction and reflectometry, superconducting quantum interference magnetometry, Raman spectroscopy and temperature dependent resistivity. The sample properties were compared to bulk magnetite, which acts as a quality standard. In particular, the Verwey transition is highly sensitive to material stoichiometry and defects. Optimized thin films exhibit an extremely sharp Verwey transition, in both magnetic and resistive measurments, between 119 K and 132 K. We have further established a sputtering process, which allows for a kinetically controlled growth of iron oxide phases ranging from α-Fe₂O₃ to Fe₃O₄+ Fe.

The authors thank LOEWE-Centre of Excellence AdRIA for financial support and Dr. Emanuel Ionescu for his time and help with Microraman measurements.