Understanding the role of oxygen vacancies in a spintronics semiconductor

Polarised neutron reflectivity data as a function of oxygen deficiency

Polarised neutron reflectivity data and model calculations as a function of oxygen deficiency. The inset shows the crystal structure of stoichiometric EuO.
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Electron-doped europium oxide (EuO) is a semiconductor which undergoes a simultaneous ferromagnetic and metal-to-insulator phase transition, across which the resistivity drops by 8 to 13 orders of magnitude.

The conduction electrons are nearly 100% spin polarized, making EuO an excellent material for next generation spintronic devices – devices in which the spins of the electrons are exploited instead of, or as well as, their charge.

An unanswered question is what effect electron doping has on the interactions and, crucially, on the degree of spin polarisation. By combining polarised neutron reflectometry with magnetometry and crystallography, we have been able to obtain precise values of oxygen-vacancy concentrations and relate this quantity to the enhanced magnetic moment in thin films and the increase in conduction-band polarisation. The results indicate that electron doping mediates an additional ferromagnetic interaction leading to an increase in ordering temperature, a result confirmed using theoretical models. These insights help to provide a fundamental understanding of the interactions in this fascinating material, as well as suggesting ways of increasing the ordering temperature in similar materials. Polarised neutron reflectivity data and model calculations as a function of oxygen deficiency. The inset shows the crystal structure of stoichiometric EuO.

PMDS Monteiro, M Barbagallo, N-J Steinke, A Ionescu, CHW Barnes, NDM Hine (University of Cambridge), CJ Kinane, TR Charlton, S Langridge (ISIS)

Research date: August 2011

Further Information

Contact: Dr A. Ionescu, e-mail: ai222@cam.ac.uk
Further reading: M. Barbagallo et al., Phys. Rev. B. 84 (2011) 075219

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