Shingo Ikeda

Principal axis rotation of magnetoresistance in α-EDT-TTF[Ni(dmit)2] salt

Abstract The transverse magnetoresistance of α-EDT-TTF[Ni(dmit) 2 ] was investigated with the magnetic field rotated within a conducting ab-plane. It was found that the magnetic-field-orientation dependence of the magnetoresistance, δ R ( B )/ R (0) has the form P sin 2 (θ-δ)+ Q cos 2 (θ-δ), where θ is the angle between b-axis and magnetic field direction and ( P , Q , δ) are temperature dependent parameters. By examining the results based on the classical theory of magnetoresistance, it was concluded that the electrical conduction in this salt is made by both EDT-TTF and Ni(dmit) 2 above 20K, mainly by Ni(dmit) 2 below 10K.

A light-emitting diode fabricated from horse-heart cytochrome c

We have fabricated a light-emitting diode from horse-heart cytochrome c and measured the electro-luminescence (EL) spectra. The spectra exhibit broad peaks around 530 and 690 nm, and a weak shoulder around 410 nm. The EL spectra are completely different from the photo-luminescence spectra previously reported. The appearance of the 690 nm emission band suggests the charge-transfer between the iron and the axial methionine ligand plays a crucial role in the electrical conduction in the cytochrome c film.

Shubnikov-De Haas effect of α-Et2Me2N[Ni(dmit)2]2 salt

Abstract Magnetoresistance of organic conductor, α-Et 2 Me 2 N[Ni(dmit) 2 ] 2 , was measured for the magnetic field along a ∗ -axis up to 23 T in the temperature down to 0.5 K. Three different types of closed orbits (α-, β-, γ-orbit) of two-dimensional Fermi surface were found through Shubnikov-de Haas oscillation. The areas of these three closed orbits are estimated to be 0.23% (α-orbit), 4.60% (β-orbit), 87.4% (γ- orbit) of the first Brillouin zone. The cyclotron masses for α-, β-, γ-orbit are estimated to be (0.06±0.01) m e , (0.166±0.01) m e , (4.3±0.2) m e , respectively.

Magnetoresistance of α -Et2Me2N[Ni (dmit)2]2 salt

Abstract The angular dependent magnetoresistance oscillation and Shubnikov-de Haas (SdH) effect were observed in α -Et 2 Me 2 N[Ni(dmit) 2 ] 2 . The former data showed magic angles, θ n characterized by tan(θ n-90)=(-0.5+n) × 0.47 (n:integer). The data of the SdH effect revealed the existence of two types of oscillations. From the period of the resistance oscillation vs. the inverse magnetic field, the cross-sectional areas of the Fermi surfaces perpendicular to the a ∗ -axis, associated with these two types of oscillations, are estimated to be ∼ 0.23% and ∼ 4.5% of the two dimensional Brillouin zone, respectively. The angular dependence of the SdH fundamental field shows two-dimensional nature of the band structure.

Magnetotransport study of α-Me2Et2N[Ni(dmit)2]2 and related materials

Abstract Magnetoresistance of organic conductor, α-Me 2 Me 2 N[Ni(dmit) 2 ] 2 , was measured for the magnetic field along a∗-axis. We found four different types of closed orbits (α-, β-, γ-, σ) through Shubnikov-de Haas (SdH) oscillation. The areas of these four closed orbits are estimated to be 0.23%, 4.6%, 87.4%, 11.3% of first Brillouin zone, respectively. The results are consistent with the band structure recently derived from the crystal structure at 11K. Contrary to α-Me 2 Et 2 N[Ni(dmit) 2 ] 2 , α-C 7 H 16 N[Ni(dmit) 2 ] 2 shows neither angular dependent magnetoresistance oscillation nor SdH oscillation for the magnetic field up to 8 T.

Novel Electroluminescence Properties of Thin Films Using Soluble Metallophthalocyanine Salts

We have prepared organic thin films of soluble dicyano(phthalocyaninato)iron salt, [(n-C7H15)4N][FeIII(Pc)(CN)2], and fabricated the electroluminescence (EL) devices having the Metal-Insulator-Metal structure. The device exhibits emission for both positive and negative bias voltages. We observed two bands in the EL spectra. One band was assigned to the Q band of the phthalocyanine molecule. The other, which shifts with changing the applied voltage, could correspond to the metal-to-ligand charge transfer (MLCT) band and/or the ligand-to-metal charge transfer (LMCT) band.

Magnetoresistance of α-ET2Me2N[Ni(dmit)2]2 salt

Abstract The angular dependent oscillation of magnetoresistance and Shubunikov-de Haas (SdH) Effect were observed on α-Et 2 Me 2 N[Ni(dmit) 2 ] 2 . The former showed magic angels, θ n characterized by tan( θ n −90°)=0.47×(−0.5+n), tan( φ m −90°)=0.30×m (n,m:integer), where θ n is the angle between c-axis and magnetic field direction within a ∗ c plane, and where φ m the angle between b-axis and magnetic field direction within a ∗ b plane. The latter revealed the existence of two types of oscillations. From the period of the resistance oscillations vs. the inverse magnetic field, the cross-sectional areas of the Fermi surfaces perpendicular to the a ∗ -axis, associated with these two types of oscillations, are estimated to be 0.23% and 4.5% of the two-dimensional Brillouin zone, respectively. The cyclotron mass and the Dingle temperature of the larger closed orbit were estimated to be 0.16m e and 11.2K, respectively.