N. Hanasaki

A new molecular superconductor β′-Et2Me2P[Pd(dmit)2]2 (dmit = 2-thioxo-1,3-dithiole-4,5-dithiolate)

Abstract The anion radical salt β′-Et 2 Me 2 P[Pd(dmit) 2 ] 2 is non-metallic at ambient pressure. An application of pressure induces a metallic behavior and the system exhibits a superconducting transition in the pressure region of 6.9–10.4 kbar with T c = 4.0−1.8 K (onset). Under higher pressure, however, non-metallic behavior appears in the low-temperature region. The isostructural salt β′-Et 2 Me 2 Sb[Pd(dmit) 2 ] 2 also shows pressure-induced metallic behavior. However, not a superconducting transition above 1.6 K, nor a high-pressure non-metallic behavior is observed at pressures up to 16.4 kbar. These Pd(dmit) 2 salts can be characterized by an existence of two different types of bands near the Fermi level. The counter cation dependence of the electronic state under pressure suggests that dimensionality of the electronic structure plays an important role.

Giant Negative Magnetoresistance Reflecting Molecular Symmetry in Dicyano(phthalocyaninato)iron Compounds

Materials containing Fe(Pc)(CN) 2 dicyano(phthalocyaninato)iron molecules show a giant negative magnetoresistance from the interaction between the conduction and the local moment. Under a magnetic field, the resistance becomes two orders of magnitude smaller than the zero-field resistance. The magnetic-field-angle dependence of the magnetoresistance reflects the symmetry of the Fe(Pc)(CN) 2 molecule. We discuss, according to the scaling relation, the correlation between the magnetoresistance and the molecular spin fluctuation.

Contribution of Degenerate Molecular Orbitals to Molecular Orbital Angular Momentum in Molecular Magnet Fe(Pc)(CN)2

We measured the static magnetic susceptibility and the electron spin resonance of the Fe(Pc)(CN) 2 complexes, and investigated the molecular magnetism of the unit Fe(Pc)(CN) 2 . The magnetic susceptibility shows a highly anisotropic Curie behavior. Based on the electron spin resonance, we found a highly anisotropic g -value ( g 1 = 3.62, g 2 = 1.11, and g 3 = 0.52) in the molecular unit Fe(Pc)(CN) 2 . This anisotropy is caused by the molecular orbital angular momentum in the degenerate next highest occupied molecular orbitals of the molecular unit Fe(Pc)(CN) 2 . Since the molecular unit Fe(Pc)(CN) 2 has a unique structure with fourfold symmetry, the molecular orbital angular momentum has a finite value of l z ∼+1 and -1. The anisotropic molecular magnetism of the unit Fe(Pc)(CN) 2 contributes the highly anisotropic Curie behavior. The molecular unit Fe(Pc)(CN) 2 is a good candidate for a molecular magnet having high magnetic anisotropy.

Charge disproportionation in highly one-dimensional molecular conductor TPP[Co(Pc)(CN)2]2

We investigated the ground state of a highly one-dimensional conductor, TPP[Co(Pc)(CN) 2 ] 2 (TPP = tetraphenylphosphonium and Pc = phthalocyanine), by the measurement of the X-ray diffraction, electron spin resonance, nuclear quadrupole resonance, and magnetoresistance. An increase of the magnetic fluctuations was observed below 20 K, where no structural deformation was detected. In the 59 Co nuclear quadrupole resonance, we found an asymmetric broadening of the spectra owing to the intrinsic inhomogeneity of the molecular charge. We propose that the ground state is characterized by a weak charge disproportionation with antiferromagnetic fluctuations due to the high one dimensionality. A large magnetoresistance was observed under a high magnetic field. Spin effects are dominant at low fields. The anisotropic magnetoresistance suggests a change in the ground-state nature above 10 T.

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.

Magneto-optical effect induced by spin chirality of the itinerant ferromagnet Nd2Mo2O7

It is demonstrated both theoretically and experimentally that the spin chirality associated with a noncoplanar spin configuration produces a magneto-optical effect. Numerical study of the two-band Hubbard model on a triangle cluster shows that the optical Hall conductivity

One-dimensional π–d electron system in TPP[Fe(Pc)(CN)2]2, [PXX][Fe(Pc)(CN)2], and (PTMA)x[Fe(Pc)(CN)2]Y(CH3CN): electron spin resonance and negative magnetoresistance

{\ensuremath{\sigma}}_{xy}(\ensuremath{\omega})

Upper critical field of the molecular superconductor β′−Et2Me2P[Pd(dmit)2]2

is proportional to the spin chirality. The detailed comparative experiments on pyrochlore-type molybdates

Magnetic Properties of d-π Conducting System, TPP[FeIIIxCoIII1-x(Pc)(CN)2]2

{R}_{2}{\mathrm{Mo}}_{2}{\mathrm{O}}_{7}

Torque study of TPP[Fe(Pc)(CN)2]2 (TPP = tetraphenyl phosphonium and Pc = phthalocyanine)

with