Navickas, M;
Giriunas, L;
Kalendra, V;
Biktagirov, T;
Gerstmann, U;
Schmidt, WG;
Maczka, M;
... Simenas, M; + view all
(2020)
Electron paramagnetic resonance study of ferroelectric phase transition and dynamic effects in a Mn²⁺ doped [NH₄][Zn(HCOO)₃] hybrid formate framework.
Physical Chemistry Chemical Physics
, 22
(16)
pp. 8513-8521.
10.1039/d0cp01612h.
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Abstract
We present an X- and Q-band continuous wave (CW) and pulse electron paramagnetic resonance (EPR) study of a manganese doped [NH4][Zn(HCOO)3] hybrid framework, which exhibits a ferroelectric structural phase transition at 190 K. The CW EPR spectra obtained at different temperatures exhibit clear changes at the phase transition temperature. This suggests a successful substitution of the Zn2+ ions by the paramagnetic Mn2+ centers, which is further confirmed by the pulse EPR and 1H ENDOR experiments. Spectral simulations of the CW EPR spectra are used to obtain the temperature dependence of the Mn2+ zero-field splitting, which indicates a gradual deformation of the MnO6 octahedra indicating a continuous character of the transition. The determined data allow us to extract the critical exponent of the order parameter (β = 0.12), which suggests a quasi two-dimensional ordering in [NH4][Zn(HCOO)3]. The experimental EPR results are supported by the density functional theory calculations of the zero-field splitting parameters. Relaxation time measurements of the Mn2+ centers indicate that the longitudinal relaxation is mainly driven by the optical phonons, which correspond to the vibrations of the metal–oxygen octahedra. The temperature behavior of the transverse relaxation indicates a dynamic process in the ordered ferroelectric phase.
| Type: | Article |
|---|---|
| Title: | Electron paramagnetic resonance study of ferroelectric phase transition and dynamic effects in a Mn²⁺ doped [NH₄][Zn(HCOO)₃] hybrid formate framework |
| Open access status: | An open access version is available from UCL Discovery |
| DOI: | 10.1039/d0cp01612h |
| Publisher version: | https://doi.org/10.1039/d0cp01612h |
| Language: | English |
| Additional information: | This version is the author accepted manuscript. For information on re-use, please refer to the publisher’s terms and conditions. |
| UCL classification: | UCL UCL > Provost and Vice Provost Offices > UCL BEAMS UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > London Centre for Nanotechnology |
| URI: | https://discovery.ucl.ac.uk/id/eprint/10113993 |
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