2D nature of magnetic states at SnO2 surfaces: a combined experimental and theoretical study

• Published in: RSC advances 2024-04, Vol.14 (19), p.13583-13590
• Main Authors: Nguyen, Hoa Hong, Friák, Martin, Pazourek, Petr, Nguyen Sy Pham, Tran, Quynh Nhu, Kiaba, Michal, Gazdová, Kristýna, Pavlů, Jana
• Format: Article
• Language: English
• Subjects: Chemistry; Configurations; Diamagnetism; Ferromagnetism; Magnetic properties; Mathematical analysis; Oxygen atoms; Room temperature; Rutile; Surface stability; Thickness; Thin films; Tin; Tin dioxide
• ISSN: 2046-2069
• DOI: 10.1039/d4ra00734d

For undoped SnO2, room temperature ferromagnetism could be seen uniquely in 2-dimensional configurations, particularly in ultra-thin films (whose thickness is ideally below 100 nm). Both bulk samples and nano-powders of pristine SnO2 are diamagnetic, indicating that a 2D surface is a key point in shaping up the magnetic properties in SnO2. As a complement to our experiments, we have performed a series of quantum-mechanical calculations for the bulk rutile-structure SnO2 as well as its (001) and (101) surfaces. The calculations included several atomic configurations with and without vacancies in/under the studied surfaces. The stability of the non-magnetic ground state of rutile SnO2 bulk was cross-checked and confirmed by its phonon spectrum computed within the harmonic approximation. Regarding the surfaces, the bulk-like (001) surface containing Sn vacancies has turned out to be ferromagnetic, while the shift of Sn vacancies under the surface resulted in a more complex ferrimagnetic state. The bulk-like (001) surface without vacancies and that with the O vacancies are predicted to be non-magnetic. Regarding the (101) surfaces, those terminated by a single layer of oxygen atoms and those terminated by tin atoms are non-magnetic, while a surface terminated by two layers of oxygen has turned out to be ferromagnetic.