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B. Arndt, B. Lechner, A. Bourgund, E. Gránäs, M. Creutzburg, K. Krausert, J. Hulva, G. Parkinson, M. Schmid, V. Vonk., F. Esch, A. Stierle:
"Order-disorder phase transition of the subsurface cation vacancy reconstruction on Fe₃O₄(001)";
Physical Chemistry Chemical Physics, 22 (2020), 8336 - 8343.

We present surface X-ray diffraction and fast scanning tunneling microscopy results to elucidate thenature of the surface phase transition on magnetite (001) from affiffiffi2p ffiffiffi2p R45 reconstructed to anon-reconstructed surface around 720 K.In situsurface X-ray diffraction at a temperature above thephase transition, at which long-range order is lost, gives evidence that the subsurface cation vacancyreconstruction still exists as a local structural motif, in line with the characteristics of a 2D second-orderphase transition. Fast scanning tunneling microscopy results across the phase transition underpin thehypothesis that the reconstruction lifting is initiated by surplus Fe ions occupying subsurface octahedralvacancies. The reversible near-surface iron enrichment and reduction of the surface to stoichiometriccomposition is further confirmed byin situlow-energy ion scattering, as well as ultraviolet and X-rayphotoemission results.

http://dx.doi.org/10.1039/d0cp00690d

https://pubs.rsc.org/en/content/articlelanding/2020/CP/D0CP00690D#!divAbstract