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| Main Authors: | , , , , , , , , , , |
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| Format: | Preprint |
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2021
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| Subjects: | |
| Online Access: | https://arxiv.org/abs/2104.04454 |
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| _version_ | 1866916493231390720 |
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| author | Canossa, Stefano Ferrari, Elena Sippel, Pit Fischer, Jonas K. H. Pfattner, Raphael Frison, Ruggero Masino, Matteo Mas-Torrent, Marta Lunkenheimer, Peter Rovira, Conceptió Girlando, Alberto |
| author_facet | Canossa, Stefano Ferrari, Elena Sippel, Pit Fischer, Jonas K. H. Pfattner, Raphael Frison, Ruggero Masino, Matteo Mas-Torrent, Marta Lunkenheimer, Peter Rovira, Conceptió Girlando, Alberto |
| contents | We present an extension and revision of the spectroscopic and structural data of the mixed stack charge transfer (CT) crystal 3,3$^\prime$,5,5$^\prime$-tetramethylbenzidine--tetrafluoro-tetracyanoquinodimethane (TMB-TCNQF4), associated with new electric and dielectric measurements. Refinement of syncrotron structural data at low temperature has led to revise the previously reported [Phys. Rev. Mat. 2, 024602 (2018)] $C2/m$ structure. The revised structure is $P2_1/m$, with two dimerized stacks per unit cell, and is consistent with the vibrational data. However, polarized Raman data in the low-frequency region also indicate that by increasing temperature above 200 K the structure presents an increasing degree of disorder mainly along the stack axis. X-ray diffraction data at room temperature have confirmed that the correct structure is $P2_1/m$ -- no phase transitions -- but did not allow to definitely substantiate the presence of disorder. On the other hand, dielectric measurement have evidenced a typical relaxor ferroelectric behavior already at room temperature, with a peak in real part of dielectric constant $ε'(T,ν)$ around 200 K and 0.1 Hz. The relaxor behavior is explained in terms of the presence of spin solitons separating domains of opposite polarity that yield to ferroelectric nanodomains. TMB-TCNQF4 is confirmed to be a narrow gap band semiconductor ($E_a \sim 0.3$ eV) with room temperature conductivity of $\sim 10^{-4}~ Ω^{-1}$ cm$^{-1}$. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2104_04454 |
| institution | arXiv |
| publishDate | 2021 |
| record_format | arxiv |
| spellingShingle | Tetramethylbenzidine-TetrafluoroTCNQ: A narrow-gap semiconducting salt with room temperature relaxor ferroelectric behavior Canossa, Stefano Ferrari, Elena Sippel, Pit Fischer, Jonas K. H. Pfattner, Raphael Frison, Ruggero Masino, Matteo Mas-Torrent, Marta Lunkenheimer, Peter Rovira, Conceptió Girlando, Alberto Materials Science We present an extension and revision of the spectroscopic and structural data of the mixed stack charge transfer (CT) crystal 3,3$^\prime$,5,5$^\prime$-tetramethylbenzidine--tetrafluoro-tetracyanoquinodimethane (TMB-TCNQF4), associated with new electric and dielectric measurements. Refinement of syncrotron structural data at low temperature has led to revise the previously reported [Phys. Rev. Mat. 2, 024602 (2018)] $C2/m$ structure. The revised structure is $P2_1/m$, with two dimerized stacks per unit cell, and is consistent with the vibrational data. However, polarized Raman data in the low-frequency region also indicate that by increasing temperature above 200 K the structure presents an increasing degree of disorder mainly along the stack axis. X-ray diffraction data at room temperature have confirmed that the correct structure is $P2_1/m$ -- no phase transitions -- but did not allow to definitely substantiate the presence of disorder. On the other hand, dielectric measurement have evidenced a typical relaxor ferroelectric behavior already at room temperature, with a peak in real part of dielectric constant $ε'(T,ν)$ around 200 K and 0.1 Hz. The relaxor behavior is explained in terms of the presence of spin solitons separating domains of opposite polarity that yield to ferroelectric nanodomains. TMB-TCNQF4 is confirmed to be a narrow gap band semiconductor ($E_a \sim 0.3$ eV) with room temperature conductivity of $\sim 10^{-4}~ Ω^{-1}$ cm$^{-1}$. |
| title | Tetramethylbenzidine-TetrafluoroTCNQ: A narrow-gap semiconducting salt with room temperature relaxor ferroelectric behavior |
| topic | Materials Science |
| url | https://arxiv.org/abs/2104.04454 |