Oxide heterostructures displaying interfacial magnetic order have been the subject of much study but their use is currently limited by low magnetic ordering temperatures. In the May 5 online edition of Chemistry of Materials (DOI: 10.1021/cm200454z), S.-K. Kim at Seoul National University and his colleagues report on the growth of (111)-oriented Sr2FeRuO3 superlattices having a robust ordered-double-perovskite structure that display magnetic ordering up to 390 K.
The researchers managed to overcome thermodynamic barriers to (111)-oriented growth by using a thin SrRuO3 buffer layer deposited on Ti4+-terminated SrTiO3 (111) as a template. They then deposited 55 alternating layers of SrFeO3 and SrRuO3 to build up a superlattice while maintaining precise structural and chemical control over each layer.
Using a combination of reflection high energy electron diffraction, x-ray diffraction, and transmission electron microscopy, the researchers confirmed the structure of the superlattices. They probed the temperature-dependent magnetization of the structure and found that it possesses a magnetic-ordering (ferromagnetic or ferrimagnetic) critical temperature (T c) of ~390 K, more than double the T c of isolated SrRuO3 and SrFeO3. They attribute this unusual behavior to band broadening and electron transfer that typically occur in ordered double perovskites, as well as ferromagnetic order stabilized by the addition of Ru5+ ions.
Ordered-double-perovskite structure of Sr2FeRuO3 shows stacking of Ru and Fe ions in (111) planes. Reprinted with permission from Chem. Mater. (May 5, 2011), DOI: 10.1021/cm200454z. ©2011 American Chemical Society.
The researchers said that their (111)-ordered superlattice-growth method may be applied to the growth of different oxide systems to achieve new kinds of room-temperature electronic and magnetic ordering.
