Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
-(BEDT-TTF)
ICl by inelastic neutron scatteringKawamura, Seiko; Matsuura, Masato*; Iguchi, Satoshi*; Sasaki, Takahiko*; Taniguchi, Hiromi*; Kubota, Aiko*; Sato, Kazuhiko*; Inamura, Yasuhiro; Kikuchi, Tatsuya*; Nakajima, Kenji
no journal, ,
It has been reported that in a molecular dimer-Mott insulator -(BEDT-TTF)ICl shows a relaxor-like dielectric response. The system exhibits a glassy ferroelectric state associated with charge disproportionation within the dimer, where a hole (
= 1/2) is localized, below 
= 62K, and a long-range antiferromagnetic order below 
= 22K. For such molecule-based materials, it is expected that low-energy phonon modes are coupled with spin/charge degrees of freedom. In order to observe the phonon modes in this system, we have performed inelastic neutron scattering measurements in a wide wave-vector and energy region using a chopper spectrometer AMATERAS at J-PARC MLF. The lowest energy mode shows remarkable temperature dependence of its intensity, while any softening is not observed. The result suggests that this phonon mode reflects changes in the spin/charge dynamics.
-(BEDT-TTF)ICl coupled with charge and spin studied by inelastic neutron scatteringKawamura, Seiko; Matsuura, Masato*; Iguchi, Satoshi*; Sasaki, Takahiko*; Taniguchi, Hiromi*; Kubota, Aiko*; Sato, Kazuhiko*; Inamura, Yasuhiro; Kikuchi, Tatsuya*; Nakajima, Kenji
no journal, ,
-(BEDT-TTF)ICl is an organic dimer-Mott insulator which exhibits a glassy ferroelectric state below = 62K and an antiferromagnetic order below = 22K. It is expected in such molecule-based materials that low-energy phonon modes lie in the energy region of charge and spin, and then the lattice is expected to couple with charge and spin degrees of freedom. To observe such phonon modes in this system, we have performed inelastic neutron scattering study using a chopper spectrometer AMATERAS installed at J-PARC MLF. The system shows the lowest-energy optical phonon mode at 
= 4.2 meV. which is significantly related to the charge degree of freedom. Analyzing the data more in detail, the intensity of the 4.2 meV-mode monotonically increases with lowering temperature toward , becomes constant below and drastically increases below . The behavior of the optical phonons at some representative 
positions are reported.
MeSb[Pd(dmit)] studied by 
SRKawamura, Seiko; Guerin, L.*; Watanabe, Isao*; Kato, Reizo*
no journal, ,
Anion radical salt 
[Pd(dmit)] ( is a counter cation) has a two-dimensional isotropic/distorted triangular lattice structure formed by Pd(dmit) dimers. Spin-1/2 is localized at each dimer in an insulating phase. One of them, EtMeSb[Pd(dmit)], has been suggested to exhibit an isotropic triangular lattice structure and to occur a first-order transition to charge separation accompanying with formation of spin-singlet state at 
= 70 K. We have obtained the evidence for the appearance of the spin-singlet state from previous muon spin relaxation (SR) measurements on this system. However, the temperature at which the muon spin relaxation rate shows an anomaly was slightly different from suggested one. Recently, a high-resolution X-ray structure analysis reported that this system exhibits an incommensurate structure phase below 
= 105 K and a commensurate charge separation phase below 
= 66.5 K. We performed additional SR study, and observed a slight increase in dynamical component below and an obvious enhancement of the dynamical fluctuation below .
MeSb[Pd(dmit)] studied by SRKawamura, Seiko; Guerin, L.*; Watanabe, Isao*; Kato, Reizo*
no journal, ,
Molecule-based organic conductor EtMeSb[Pd(dmit)] is a two-dimensional triangular lattice system with spin-1/2. The system is suggested to undergo a first order transition to a charge separation (CS) phase with formation of a spin-singlet state at = 70 K. Recently, it was found by a high-resolution X-ray diffraction measurement that an intermediate incommensurate phase, where the degree of spatial distortion of the triangular lattice is modulated, appears below = 105 K and then the commensurate CS phase appears below = 66.5 K. We performed SR measurements on this system to investigate magnetic dynamics in the incommensurate and commensurate phases. A small enhancement of the muon spin relaxation was observed below , in addition to a drastic increase in the muon spin relaxation rate below . Our result may indicate that the magnetic correlation significantly coupled with the lattice structure changes at .