This article is cited in 4 papers

Dielectrics

Paramagnetic mn antisite defects in nanoceramics of aluminum–magnesium spinel

A. F. Zacepin^a, A. N. Kiryakov^a, D. R. Bajtimirov^a, T. V. D'yachkova^b, A. P. Tyutyunnik^b, Yu. G. Zainulin<sup>b

a</sup> Ural Federal University, Ekaterinburg
^b Institute of Solid State Chemistry, Urals Branch of the Russian Academy of Sciences, Ekaterinburg

Abstract: 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 $\sim$ 30 nm) are obtained by thermobaric synthesis. Microcrystalline ceramics and MgAl$_{2}$O$_{4}$ single crystal are used as the reference samples. Characteristic paramagnetic centers of Mn$^{2+}$ (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 Mn$^{2+}$ 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 Mn$^{2+}$ centers in nanoceramics significantly differ on that in microceramics and single crystal. EPR signal of Mn$^{2+}$ centers in nanoceramics is characterized by two anomalous constant HFS ($A_1$ = 91.21 G, $A_2$ = 87.83 G) caused by two types of octahedrally coordinated manganese ions ([Mn$^{2+}$]$_{\mathrm{Al}^{3+}}$ antisite defects). The features of spectral parameters of manganese centers correlate with a decrease in the cell parameter of MgAl$_{2}$O$_{4}$ in the nanostructural state. The observed effects are interpreted based on the assumed scheme of [Mn$^{2+}$]$_{\mathrm{Al}^{3+}}$ charge compensation by the aluminum antisite defect and F$^+$ center.

Keywords: electron paramagnetic resonance, MgAl$_{2}$O$_{4}$, nanoceramics, microceramics, hyperfine structure, antisite defects.

Received: 16.08.2019
Revised: 16.08.2019
Accepted: 03.09.2019

DOI: 10.21883/FTT.2020.01.48744.568

 English version: Physics of the Solid State, 2020, 62:1, 137–143

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