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  Martí, X.; Ferrer, P.; Herrero-Albillos, J.; Narvaez, J.; Holy, V.; Barrett, N.; Alexe, M.; Catalan, G.: Skin layer of BiFeO₃ single crystals. Physical Review Letters 106 (2011), p. 236101/1-4

10.1103/PhysRevLett.106.236101

Abstract:
A surface layer (‘‘skin’’) different from the bulk was found in single crystals of BiFeO3. Impedance analysis and grazing incidence x-ray diffraction reveal a phase transition at T
 275  5 C that is confined within the surface of BiFeO3. X-ray photoelectron spectroscopy and refraction-corrected x-ray diffraction as a function of incidence angle and photon wavelength indicate a reduced electron density and an elongated out-of-plane lattice parameter within a few nanometers of the surface. The skin will affect samples with large surface to volume ratios, as well as devices that rely on interfacial coupling such as exchange bias.