Paramagnetic Mn Antisite Defects in Nanoceramics of Aluminum–Magnesium Spinel

Autor: A. F. Zatsepin, T. V. D'yachkova, D. R. Baytimirov, Alexander P. Tyutyunnik, Yu. G. Zainulin, A. N. Kiryakov
Rok vydání: 2020
Předmět:
Zdroj: Physics of the Solid State. 62:137-143
ISSN: 1090-6460
1063-7834
Popis: The effect of structure and size parameters on the formation of intrinsic and impurity paramagnetic centers in nanoceramics of aluminum–magnesium spinel is studied. The studied samples (grain size ~30 nm) are obtained by thermobaric synthesis. Microcrystalline ceramics and MgAl2O4 single crystal are used as the reference samples. Characteristic paramagnetic centers of Mn2+ (hyperfine structure constant (HFS) A = 82 G) are present in both single crystal and microceramics. In the studied samples of nanoceramics in the initial state, both impurity Mn2+ and intrinsic F+ centers exist. Unlike the nanoceramics, the centers of F+ type in the reference sample appear only after the irradiation with accelerated electrons (130 keV). The parameters of Mn2+ centers in nanoceramics significantly differ on that in microceramics and single crystal. EPR signal of Mn2+ centers in nanoceramics is characterized by two anomalous constant HFS (A1 = 91.21 G, A2 = 87.83 G) caused by two types of octahedrally coordinated manganese ions ([Mn2+]$$_{{{\text{A}}{{{\text{l}}}^{{{\text{3 + }}}}}}}$$ antisite defects). The features of spectral parameters of manganese centers correlate with a decrease in the cell parameter of MgAl2O4 in the nanostructural state. The observed effects are interpreted based on the assumed scheme of [Mn2+]$$_{{{\text{A}}{{{\text{l}}}^{{{\text{3 + }}}}}}}$$ charge compensation by the aluminum antisite defect and F+ center.
Databáze: OpenAIRE
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