| Article | |
| Title | Anisotropy of the Electric Field Gradient in Two-Dimensional α-MoO$_3$ Investigated by $^{57}$Mn($^{57}$Fe) Emission Mössbauer Spectroscopy |
| Author(s) | Schell, Juliana (CERN ; Duisburg-Essen U.) ; Zyabkin, Dmitry (Ilmenau Tech. U.) ; Bharuth-Ram, Krish (KwaZulu Natal U.) ; Gonçalves, João N (Aveiro U.) ; Díaz-Guerra, Carlos (Madrid U.) ; Gunnlaugsson, Haraldur P (Iceland U.) ; Martín-Luengo, Aitana Tarazaga (Linz U.) ; Schaaf, Peter (Ilmenau Tech. U.) ; Bonanni, Alberta (Linz U.) ; Masenda, Hilary (Witwatersrand U. ; Philipps U. Marburg) ; Dang, Thien Thanh (Duisburg-Essen U.) ; Mølholt, Torben E (CERN) ; Ólafsson, Sveinn (Iceland U.) ; Unzueta, Iraultza (Basque U., Bilbao) ; Mantovan, Roberto (IMM, Bologna) ; Johnston, Karl (CERN) ; Gíslason, Hafliði P (Iceland U.) ; Krastev, Petko B (Sofiya, Inst. Nucl. Res.) ; Naidoo, Deena (Witwatersrand U.) ; Qi, Bingcui (Iceland U.) |
| Publication | 2022 |
| Number of pages | 13 |
| In: | Crystals 12 (2022) 942 |
| DOI | 10.3390/cryst12070942 |
| Subject category | Nuclear Physics - Experiment |
| Accelerator/Facility, Experiment | CERN ISOLDE |
| 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. |
| Copyright/License | © 2022-2024 the authors (License: CC-BY-4.0) |
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Záznam vytvorený 2023-03-17, zmenený 2023-03-17
