Ferroelectric phase transition in LiNaGe<sub>4</sub>O<sub>9</sub> crystal studied by EPR of Mn<SUP>4+</SUP> and optical absorption spectroscopy
The result's identifiers
Result code in IS VaVaI
<a href="https://www.isvavai.cz/riv?ss=detail&h=RIV%2F00216305%3A26620%2F26%3A0198217" target="_blank" >RIV/00216305:26620/26:0198217 - isvavai.cz</a>
Result on the web
<a href="https://pubs.aip.org/aip/jap/article/137/16/164103/3344931/Ferroelectric-phase-transition-in-LiNaGe4O9" target="_blank" >https://pubs.aip.org/aip/jap/article/137/16/164103/3344931/Ferroelectric-phase-transition-in-LiNaGe4O9</a>
DOI - Digital Object Identifier
<a href="http://dx.doi.org/10.1063/5.0264287" target="_blank" >10.1063/5.0264287</a>
Alternative languages
Result language
angličtina
Original language name
Ferroelectric phase transition in LiNaGe<sub>4</sub>O<sub>9</sub> crystal studied by EPR of Mn<SUP>4+</SUP> and optical absorption spectroscopy
Original language description
Electron paramagnetic resonance (EPR) of Mn4+ ions and optical absorption spectra are studied in the lithium-sodium tetragermanate LiNaGe4O9 crystal in the range of a ferroelectric phase transition. Anisotropy of the EPR spectra evidences that the paramagnetic Mn4+ ions are substituted for Ge hosts within oxygen octahedra. Double splitting of EPR lines below the phase transition temperature (T-C = 114 K) indicates lowering the symmetry (C-2 -> C-1) of the Mn4+ sites. The components of the g factor and hyperfine interaction tensor A, axial D, and rhombic E crystal field parameters have been determined from the EPR spectra above and below T-C. It is shown that at phase transition, the values of the spin-Hamiltonian parameters vary only slightly and the EPR spectra are changed mainly due to magnetic axes rotation. Based on this result, it is proposed that below T-C, GeO6 octahedra rotate nearly around the crystal axis b. On cooling, the angle of octahedra rotation obeys the square root temperature dependence predicted by the mean field theory of phase transitions. The low-energy part of the optical absorption edge in the LiNaGe4O9 crystal has been described by Urbach's rule. Near T-C, the parameters of Urbach's rule exhibit an anomalous deviation from the regular temperature behavior. The linear dependence of the forbidden band isoabsorption width E-g(alpha)(T) changes the slope, whereas the parameter sigma(T), determined by the strength of an electron-phonon interaction, demonstrates a sharp non-monotonic anomaly. The study of the EPR and optical absorption spectra evidences for second order of the ferroelectric phase transition in the LiNaGe4O9 crystal.
Czech name
—
Czech description
—
Classification
Type
J<sub>imp</sub> - Article in a specialist periodical, which is included in the Web of Science database
CEP classification
—
OECD FORD branch
10302 - Condensed matter physics (including formerly solid state physics, supercond.)
Result continuities
Project
<a href="/en/project/GA23-05578S" target="_blank" >GA23-05578S: Electric-field control of spin-qubits in quantum paraelectrics</a><br>
Continuities
P - Projekt vyzkumu a vyvoje financovany z verejnych zdroju (s odkazem do CEP)
Others
Publication year
2025
Confidentiality
S - Úplné a pravdivé údaje o projektu nepodléhají ochraně podle zvláštních právních předpisů
Data specific for result type
Name of the periodical
Journal of applied physics
ISSN
0021-8979
e-ISSN
1089-7550
Volume of the periodical
137
Issue of the periodical within the volume
16
Country of publishing house
US - UNITED STATES
Number of pages
12
Pages from-to
—
UT code for WoS article
001478388300009
EID of the result in the Scopus database
2-s2.0-105003322802