M. Kinoshita

Reexamination of angle dependent magnetoresistance oscillationin θ-(BEDT-TTF)2I3

Abstract It is found that the angle-dependent magnetoresistance oscillation in θ-(BEDT-TTF) 2 I 3 consists of the short-period oscillation and the long-period one. They are attributed to the magnetic breakdown orbit and the closed orbit at the Brillouin zone boundary, respectively.

Fermi surface and absence of additional mass enhancement near the insulating phase in (DMe-DCNQI)2Cu

Abstract The de Haas - van Alphen measurements of the deuterated molecular conductor (DMe-DCNQI) 2 Cu have been carried out to investigate the Fermi surface and the possibility of the mass enhancement of the conduction electrons near the insulating phase. The Fermi surfaces and the cyclotron masses of the deuterated samples which show the drastic metal - insulator - metal transition are found to be the same as those of the undeuterated sample. The fact shows that the additional mass enhancement due to many body effects is absent near the insulating phase.

Ferromagnetic resonance and nonlinear absorption in p-NPNN

Summary form only given. The FMR(Ferromagnetic Resonance) measurements have been performed on /spl beta/-phase p-NPNN(nitrophenyl nitronyl nitroxide) ferromagnetic below 0.6 K. We used an X-band resonance apparatus which can be used down to 0.5 K. We observed clear magnetostatic modes and non-linear line shapes for the as grown samples at the lowest temperature. We have also observed the effect known as the foldover effect. We should be careful about the demagnetization effect when the magnetization is large, therefore we performed the FMR measurement using nearly spherically shaped samples. We studied the temperature dependences of g-factor below 1.3 K, and found the intrinsically anisotropic behavior. This may be due to the anisotropy field along the crystal b-axis, which is consistent with the result reported by L.P. Le et at. using the /spl mu/SR measurement.

Optical properties of α′-(BEDT-TTF)2IBr2

Abstract The molecular semiconductor α′-(BEDT-TTF) 2 IBr 2 is known to undergo structural and magnetic phase transitions at around 200 K and 60 K, respectively. In order to elucidate the mechanism of these phase transitions, measurements of the polarised reflectance spectra and Raman spectra were carried out at low temperatures. In the reflectance spectra, the spectral change in the infrared region was observed at around 200 K. In the Raman spectra, the band at 1480 cm −1 splits with decreasing temperature. No change was not observed for both measurements at around 60 K. We point out the possibility that the BEDT-TTFs may posses different charges in this salt.

The Shubnikov-de Haas oscillations and a small closed orbit in θ-(BEDT-TTF)2I3

Abstract The Shubnikov-de Haas (SdH) experiments on an organic conductor θ-(BEDT-TTF) 2 I 3 have been carried out. In addition to the two SdH frequency branches due to the quasi two-dimensional Fermi surfaces, new branches due to small three-dimensional Fermi surfaces are found.

Magnetic properties of DCNQI-Cu systems

Abstract Recent advances in the study of magnetic properties of a series of molecular conductors, Cu salts of DCNQIs, are presented. First, the antiferromagnetic order of Cu spins in the insulating phases below about 10 K is found to be accompanied by weak ferromagnetism with the spontaneous moment perpendicular to the tetragonal c -axis. Second, our susceptibility study of the metal-insulator-metal (M-I-M) reentrant system, (DMe-DCNQI-α,α′- d 2 ) 2 Cu, has lead to the absence of many-body enhancement of the susceptibility in the low temperature metallic phase. Finally, (DI-DCNQI) 2 Cu is found to exhibit considerably enhanced and temperature dependent susceptibility, suggesting the effect of spin fluctuation in the metallic state.

Charge transfer and reentrant phenomenon in deuterated (DMe-DCNQI)/sub 2/Cu

Abstract Li-doping in Cu salt of deuterated DMe-DCNQI- d 7 system has shown drastic effects on physical properties. Undoped (DMe-DCNQI- d 7 ) 2 Cu exhibits a first-order metal-insulator (M-I) transition at 80K, and the Li salt, which is isostructural with the Cu salt, is a one-dimensional (1D) conductor. A small amount of Li-doping suppresses the M-I transition. The M-I-M (reentrant) transition which is similar to that in selectively deuterated (DMe-DCNQI) 2 Cu appears in a narrow region of Li contents x . The x — T phase diagram under ambient pressure well reproduces P - T phase diagram of (DMe-DCNQI) 2 Cu system. Based on these results, an importance of the degree of charge transfer is described.