%0 Journal Article
%A Schell, Juliana
%A Zyabkin, Dmitry
%A Bharuth-Ram, Krish
%A Gonçalves, Joao N.
%A Díaz-Guerra Viejo, Carlos
%A Gunnlaugsson, Haraldur P.
%A Tarazaga Martín-Luengo, Aitana
%A Schaaf, Peter
%A Bonanni, Alberta
%A Masenda, Hilary
%A otros, ...
%T Anisotropy of the electric field gradient in two-dimensional alpha-MoO_(3) investigated by (57)^Mn((57)^Fe) emission mossbauer spectroscopy
%D 2022
%@ 2073-4352
%U https://hdl.handle.net/20.500.14352/73261
%X Van der Waals alpha-MoO_(3) samples offer awide range of attractive catalytic, electronic, and optical properties. We present herein an emission Mossbauer spectroscopy (eMS) study of the electric-field gradient (EFG) anisotropy in crystalline free-standing alpha-MoO_(3) samples. Although alpha-MoO3 is a twodimensional (2D) material, scanning electron microscopy shows that the crystals are 0.5-5-mu m 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 (57)^Mn (t(1/ 2) = 1.5 min), which decays to the (57)^Fe, 14.4 keV Mossbauer state. The eMS spectra of the samples are dominated by a paramagnetic doublet (D1) with an angular dependence, pointing to the Fe^(2+) 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 derWaals interactions in the 2D material. Moreover, a second broad component, D2, can be assigned to Fe^(3+) 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
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