Regensburg 2010 – wissenschaftliches Programm
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MA: Fachverband Magnetismus
MA 15: Magnetic Half-metals and Oxides I
MA 15.11: Vortrag
Mittwoch, 24. März 2010, 12:45–13:00, H22
Correlation between Curie temperature and carrier density of electron-doped EuO - is there an intrinsic limit on TC? — •Thomas Mairoser1, Andreas Schmehl1, Jochen Mannhart1, Alexander Melville2, Tassilo Heeg2, Darrell G. Schlom2, Peter Böni3, Lea Canella3, and Jürgen Schubert4 — 1Universität Augsburg — 2Cornell University, USA — 3Technische Universität München — 4Forschungszentrum Jülich
The ferromagnetic semiconductor europium oxide exhibits a multitude of giant properties, such as metal-to-insulator transitions, a colossal magneto-resistance, and very pronounced magneto-optic effects. The recently demonstrated spin-polarization of >90 % in the ferromagnetic state [A. Schmehl et al., Nat. Mat. 6, 882 (2007)] and its excellent electronic compatibility with Si make it an interesting candidate for semiconductor based spintronics. Nevertheless the low Curie temperature (TC) of 69 K of undoped EuO is a major obstacle for the use of this outstanding material in commercial spintronic applications.
By electron doping EuO with donor impurities, TC can substantially be increased exploiting an additional exchange interaction that is mediated via the conduction electrons.
Here we report on measurements of TC and the carrier densities by Hall effect on La and Gd doped EuO films grown over a wide range of doping concentrations and growth conditions. The experiments show that only a small fraction of the introduced impurities actually act as donors even for optimized growth parameters. Furthermore we found a strong correlation between Curie temperatures and carrier densities.