Multistep Development of the Hyperfine Fields in λ-(BEDT-STF)₂FeCl₄ Studied by Mössbauer Spectroscopy

Magnetic state in the quasi-two-dimensional organic conductor λ−(BEST)2FeCl4 and the path of π−dSaito1, Iida2, Kobayashi3 et al. 2022Phys. Rev. BSelf Cite3080View full textAdd to dashboardCite

“…Below 26 K, the singlet peak gradually splits into sextet peaks and a residual central singlet peak, enabling the data to be fitted with a sextet and a residual singlet peak. The residual singlet peak and its gradual disappearance with decreasing temperature are characteristics which have been already observed in BETS and STF salts [28,29].…”

“…The multistep development of the hyperfine fields, including the absence of any anomalies in magnetic susceptibility, was almost that of λ-(STF) 2 FeCl except for the at which the fields started to develop [29]. Considering that the temperature in λ-(STF) 2 FeCl 4 corresponded to the AFM transition temperature in the donor layer [19], λ-(BEST) 2 FeCl 4 undergoes a magnetic transition at around 26 K in the donor layer.…”

“…However, the three salts are isostructural and insulators at low temperatures. In fact, the magnetization, specific heat, and Mössbauer spectra of STF salt at low temperatures show the same behavior as those of BETS salt [17,18,28,29,32]. Since the number of selenium atoms in the STF molecule is reduced from that in the BETS molecule, the π -d interaction of λ-(STF) 2 FeCl 4 is expected to be smaller than that of λ-(BETS) 2 FeCl 4 .…”

Antiferromagnetic ordering of organic Mott insulator $λ$-(BEDSe-TTF)$_2$GaCl$_4$

“…The reason for the absence of magnetic order may be the quantum critical effect of λ-STF being located between the AF and superconducting phases [27], or the disorder effect originating from the asymmetric BEDT-STF molecules. In contrast, AF order has been observed in λ-(BETS) 2 FeCl 4 [28,29] and λ-(STF) 2 FeCl 4 [30][31][32], although there is a contribution of 3d spins from Fe ions. To understand why λ-STF does not exhibit any magnetic ordering, physical properties in λ-ET that does not contain asymmetry in its donor molecule should be investigated under pressure.…”

“…λ-(BETS) 2 FeCl 4 exhibits a field-induced superconductivity [12] and a strange metal-insulator transition with AF ordering [69], whereas λ-(STF) 2 FeCl 4 shows a unique magnetic response, in which the magnetization processes between π and 3d spin systems are different in the AF state [30][31][32]. In these Fe-containing systems, the π-d interaction plays an essential role in the physical properties.…”