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- Title
Anisotropy of the Electric Field Gradient in Two-Dimensional α-MoO 3 Investigated by 57 Mn(57 Fe) Emission Mössbauer Spectroscopy.
- Authors
Schell, Juliana; Zyabkin, Dmitry; Bharuth-Ram, Krish; Gonçalves, João N.; Díaz-Guerra, Carlos; Gunnlaugsson, Haraldur P.; Martín-Luengo, Aitana Tarazaga; Schaaf, Peter; Bonanni, Alberta; Masenda, Hilary; Dang, Thien Thanh; Mølholt, Torben E.; Ólafsson, Sveinn; Unzueta, Iraultza; Mantovan, Roberto; Johnston, Karl; Gíslason, Hafliði P.; Krastev, Petko B.; Naidoo, Deena; Qi, Bingcui
- Abstract
Van der Waals α-MoO3 samples offer a wide range of attractive catalytic, electronic, and optical properties. We present herein an emission Mössbauer spectroscopy (eMS) study of the electric-field gradient (EFG) anisotropy in crystalline free-standing α-MoO3 samples. Although α-MoO3 is a two-dimensional (2D) material, scanning electron microscopy shows that the crystals are 0.5–5-µm thick. The combination of X-ray diffraction and micro-Raman spectroscopy, performed after sample preparation, provided evidence of the phase purity and crystal quality of the samples. The eMS measurements were conducted following the implantation of 57Mn (t1/2 = 1.5 min), which decays to the 57Fe, 14.4 keV Mössbauer state. The eMS spectra of the samples are dominated by a paramagnetic doublet (D1) with an angular dependence, pointing to the Fe2+ probe ions being in a crystalline environment. It is attributed to an asymmetric EFG at the eMS probe site originating from strong in-plane covalent bonds and weak out-of-plane van der Waals interactions in the 2D material. Moreover, a second broad component, D2, can be assigned to Fe3+ defects that are dynamically generated during the online measurements. The results are compared to ab initio simulations and are discussed in terms of the in-plane and out-of-plane interactions in the system.
- Subjects
EMISSION spectroscopy; ELECTRIC fields; OPTICAL properties; ANISOTROPY; MOSSBAUER spectroscopy; SCANNING electron microscopy
- Publication
Crystals (2073-4352), 2022, Vol 12, Issue 7, pN.PAG
- ISSN
2073-4352
- Publication type
Article
- DOI
10.3390/cryst12070942