| Properties | |
|---|---|
| SrRuO3 | |
| Molar mass | 236.69 g/mol |
| Appearance | Black solid |
| Density | 6.5–6.7 g/cm³ |
| Melting point | 2575 K1 |
| Insoluble in water; dissolves in periodate solution2 | |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
| |
Monostrontium ruthenate (SrRuO3, SRO) is a conductive perovskite oxide with the chemical formula SrRuO3. It is one of the few known 4d transition-metal oxides that exhibits itinerant ferromagnetism and metallic conductivity. Owing to its combination of electrical conductivity, chemical stability, and compatibility with other perovskite oxides, SRO is widely used as an electrode material in oxide electronics and epitaxial heterostructures.3
History
SrRuO3 was first synthesized and characterized in the 1950s as part of broader investigations into complex oxide perovskites containing transition metals.4 Interest in the material increased substantially during the 1990s with the development of epitaxial thin-film growth techniques, which enabled the fabrication of high-quality single-crystal films.56 The discovery that SRO combines metallic conductivity with ferromagnetic ordering made it an important model system for studying correlated-electron phenomena in oxide materials and a technologically important electrode for ferroelectric and multiferroic devices.7
Structure
SrRuO3 crystallizes in a distorted perovskite structure in which strontium occupies the A-site and ruthenium occupies the B-site of the ABO3 lattice. At room temperature, bulk SRO adopts an orthorhombic crystal structure (space group Pbnm) arising from rotations and tilts of the RuO6 octahedra.8
The crystal structure is sensitive to epitaxial strain. Thin films grown on lattice-mismatched substrates can undergo strain-induced structural distortions and may adopt tetragonal or other symmetry variants. These structural changes strongly influence the electronic and magnetic properties of the material. 9
Physical properties
Electronic transport
SrRuO3 is a metallic conductor over a wide temperature range. Unlike many transition-metal oxides, it remains metallic at low temperatures and exhibits relatively low electrical resistivity. Its transport properties reflect moderate electron-electron correlations associated with the Ru 4d electronic states.10
The electrical conductivity depends strongly on film quality, thickness, stoichiometry, and strain. Ruthenium deficiency generally increases resistivity and suppresses magnetic ordering, while high-quality epitaxial films can exhibit transport properties approaching those of bulk single crystals.11
Magnetism
SRO is an itinerant ferromagnet with a Curie temperature typically around 150–160 K. The ferromagnetism arises from partially filled Ru 4d bands and is often described using an intermediate picture between localized and itinerant magnetism.12
The material exhibits strong magnetocrystalline anisotropy, and the orientation of the magnetic easy axis depends on crystal structure, epitaxial strain, and temperature. Thin films have served as model systems for studies of magnetic domains, domain-wall transport, and current-induced domain-wall motion.13
Optical and electronic structure
Optical spectroscopy, photoemission measurements, and first-principles calculations have shown that SRO is a moderately correlated metal. Its electronic structure is dominated by hybridized Ru 4d and O 2p states near the Fermi level. Spectroscopic studies reveal quasiparticle behavior together with signatures of electron correlation and spin-dependent electronic structure.14
Applications
The combination of metallic conductivity, chemical stability, and structural compatibility with perovskite oxides has made SRO one of the most widely used electrode materials in oxide thin-film technology. SRO is frequently employed as a bottom or top electrode in epitaxial ferroelectric capacitors based on materials such as barium titanate and lead zirconate titanate15. It is also used in multiferroic heterostructures, oxide superlattices, tunnel junctions, and other devices where a conductive oxide with a close lattice match to functional perovskites is required.
Because SRO is ferromagnetic, it has also attracted interest in spintronics and magnetoelectronic devices, particularly as a model oxide ferromagnet that can be integrated into complex oxide heterostructures.
References
References
- Yamanaka, S.; Maekawa, T.; Muta, H.; Matsuda, T.; Kobayashi, S.; Kurosaki, K. (2004). "Thermophysical properties of SrHfO3 and SrRuO3". Journal of Solid State Chemistry. 177 (10). doi:10.1016/j.jssc.2004.05.039.
- Weber, D.; Vofely, R.; Chen, Y.; Mourzina, Y.; Poppe, U. (2013). "Variable resistor made by repeated steps of epitaxial deposition and lithographic structuring of oxide layers by using wet chemical etchants". Thin Solid Films. 533. arXiv:1301.4828. doi:10.1016/j.tsf.2012.11.118.
- Vailionis, A.; Siemons, W.; Koster, G. (2008). "Room-temperature epitaxial stabilization of a tetragonal phase in ARuO3 (A = Ca and Sr) thin films". Applied Physics Letters. 93 051909. doi:10.1063/1.2969401. hdl:2433/84593.
- Randall, J. J.; Ward, R. (1959). "The Preparation of Some Ternary Oxides of the Platinum Metals". Journal of the American Chemical Society. 81 (11): 2629–2631. doi:10.1021/ja01520a007.
- Eom, C. B.; Cava, R. J.; Fleming, R. M.; Wu, W.; Tyson, T. A.; van Dover, R. B.; Phillips, J. M.; Marshall, J. H.; Hsu, J. W. P. (1992). "Single-crystal epitaxial thin films of the isotropic metallic oxides Sr1−xCaxRuO3". Science. 258 (5087): 1766–1769. doi:10.1126/science.258.5089.1766.
- Choi, J.; Eom, C. B.; Rijnders, G.; Rogalla, H.; Blank, D. H. A. (2001). "Growth mode transition from layer by layer to step flow during the growth of heteroepitaxial SrRuO3 on (001) SrTiO3". Applied Physics Letters. 79: 1447–1449. doi:10.1063/1.1389837.
- Klein, L.; Marshall, A. F.; Reiner, J. W.; Ahn, C. H.; Geballe, T. H.; Beasley, M. R.; Kapitulnik, A. (1998). "Large magnetoresistance of single-crystal films of ferromagnetic SrRuO3". Journal of Magnetism and Magnetic Materials. 188 (3): 319–325. doi:10.1016/S0304-8853(98)00201-7.
- Jones, C. W.; Battle, P. D.; Lightfoot, P.; Harrison, W. T. A. (1989). "The structure of SrRuO3 by time-of-flight neutron powder diffraction". Acta Crystallographica Section C. 45 (3): 365–367. doi:10.1107/S0108270188009850.
- Zayak, A. T.; Huang, X.; Neaton, J. B.; Rabe, K. M. (2006). "Structural, electronic, and magnetic properties of SrRuO3 under epitaxial strain". Physical Review B. 74. doi:10.1103/PhysRevB.74.094104.
- Allen, P. B.; Berger, H.; Chaloupka, J.; Friedt, O.; Hussey, N. E.; McBreen, D.; Meigs, G.; Ocko, B. M.; Perry, R. S.; Schofield, A. J. (1996). "Transport properties, thermodynamic properties, and electronic structure of SrRuO3". Physical Review B. 53 (8): 4393–4398. arXiv:cond-mat/9601106. doi:10.1103/PhysRevB.53.4393.
- Koster, G.; Klein, L.; Siemons, W.; Rijnders, G.; Dodge, J. S.; Eom, C.-B.; Blank, D. H. A.; Beasley, M. R. (2012). "Structure, physical properties, and applications of SrRuO3 thin films". Reviews of Modern Physics. 84 (1): 253–298. doi:10.1103/RevModPhys.84.253.
- Kanbayasi, A. (1976). "Magnetic properties of SrRuO3". Journal of the Physical Society of Japan. 41 (6): 1876–1882. doi:10.1143/JPSJ.41.1876.
- Klein, L.; Kats, Y.; Marshall, A. F.; Reiner, J. W.; Geballe, T. H.; Beasley, M. R.; Kapitulnik, A. (2001). "Domain-wall resistivity in SrRuO3: the influence of domain walls spacing". Journal of Magnetism and Magnetic Materials. 22–26: 780–781. doi:10.1016/S0304-8853(00)00747-2.
- Mazin, I. I.; Singh, D. J. (1997). "Electronic structure and magnetism in Ru-based perovskites". Physical Review B. 56 (5): 2556–2571. arXiv:cond-mat/9702168. doi:10.1103/PhysRevB.56.2556.
- Eom, C. B.; van Dover, R. B.; Phillips, J. M.; Werder, D. J.; Marshall, J. H.; Chen, C. H.; Cava, R. J.; Fleming, R. M.; Fork, D. K. (1993). "Fabrication and properties of epitaxial ferroelectric heterostructures with SrRuO3 isotropic metallic oxide electrodes". Applied Physics Letters. 63 (5087): 2570–2572. doi:10.1063/1.110436.