Antiferromagnetic ordering of organic Mott insulator $\lambda$-(BEDSe-TTF)${}_2$GaCl${}_4$

Abstract

The band structure and magnetic properties of organic charge-transfer salt $\lambda$-(BEDSe-TTF)${}_2$GaCl${}_4$ (BEDSe-TTF: bis(ethylenediseleno)tetrathiafulvalene; abbreviated as $\lambda$-BEDSe) are investigated. The reported crystal structure is confirmed using X-ray diffraction measurements, and the transfer integrals are calculated. The degree of electron correlation $U/W$ ($U$: on-site Coulomb repulsion, $W$: bandwidth) of $\lambda$-BEDSe is larger than one and comparable to that of the isostructural Mott insulator $\lambda$-(ET)${}_2$GaCl${}_4$ (ET: bis(ethylenedithio)tetrathiafulvalene, abbreviated as $\lambda$-ET), whereas the $U/W$ of the superconducting salt $\lambda$-(BETS)${}_2$GaCl${}_4$ (BETS: bis(ethylenedithio)tetraselenafulvalene) is smaller than one. ${}^{13}$C-NMR and $\mu$SR measurements revealed that $\lambda$-BEDSe undergoes an antiferromagnetic (AF) ordering below $T_{\mathrm{N}}=22$~K. In the AF state, discrete ${}^{13}$C-NMR spectra with a remaining central peak are observed, indicating the commensurate AF spin structure also observed in $\lambda$-ET. The similarity between the structural and magnetic properties of $\lambda$-BEDSe and $\lambda$-ET suggests that both salts are in the same electronic phase, i.e., the physical properties of $\lambda$-BEDSe can be understood by the universal phase diagram of bandwidth-controlled $\lambda$-type organic conductors obtained by donor molecule substitution.

arXiv comment12 pages, 9 figures, accepted for publication in Phys. Rev. B

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Cited by in corpus (2)

• Charge-Transfer Complex $\kappa$-(BEST)${}_2$Cu${}_2$(CN)${}_3$ Analogous to Organic Spin Liquid Candidate
• Dynamics of ethylene groups and hyperfine interactions between donor and anion molecules in $\lambda$-type organic conductors studied by ${}^{69,71}$Ga-NMR spectroscopy