Dresden 2009 – scientific programme
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MA: Fachverband Magnetismus
MA 37: Spin Dependent Transport Phenomena
MA 37.16: Talk
Thursday, March 26, 2009, 19:15–19:30, HSZ 403
Spin-filtering in thin magnetic insulator barriers: EuO — •Martina Müller1,2, Guo-Xing Miao1, and Jagadeesh S. Moodera1 — 1Francis Bitter Magnet Laboratory, Massachusetts Institute of Technology, Cambridge, USA — 2Institute of Solid State Research, Research Center Jülich, Jülich, Germany
The magnetic insulator Europium Oxide (EuO) has been recognized as a promising material for the generation of highly spin-polarized currents. Its spin-filtering property is due to exchange splitting of the conductance band below the ferromagnetic transition temperature Tc. Especially challenging is to achieve sizable magnetic ordering and exchange splitting in thin (< 6 nm) EuO films, which is the thickness regime of spin-filter tunnel barriers.
In this work, we studied the magnetic and transport properties of 1 – 6 nm EuO films to explore their spin filtering efficiency. We found the EuO thickness being one of the primary factors scaling the Curie temperature Tc and the onset of the metal-insulator transition. We show, that the reduced magnetic ordering at interfaces due to structural and chemical intermixing becomes particularly relevant in the low thickness regime. Current-voltage measurements of EuO-based tunnel junctions showed a strongly bias-dependent, two-step Fowler-Nordheim-type tunneling characteristics. Moreover, we could determine an exchange splitting of φ=0.5 eV of the conduction band (CB) of 4nm EuO barriers by fully electrical means. The results show a direct correlation of the temperature-dependent change of the CB height with the EuO magnetic state.