Masafumi Tamura

Bio: Masafumi Tamura is an academic researcher from Toho University. The author has contributed to research in topics: Magnetic susceptibility & Antiferromagnetism. The author has an hindex of 22, co-authored 74 publications receiving 2184 citations. Previous affiliations of Masafumi Tamura include University of Tokyo.

Low-temperature magnetic properties of the ferromagnetic organic radical, p-nitrophenyl nitronyl nitroxide.

Abstract: Low-temperature magnetic properties of the \ensuremath{\beta} and \ensuremath{\gamma} phases of p-nitrophenyl nitronyl nitroxide (p-NPNN) were determined by measuring the specific heat, the magnetic susceptibility, and the hysteresis curve of magnetization above $^{3}\mathrm{He}$ temperature in external magnetic fields. The \ensuremath{\beta}-phase crystal undergoes a bulk ferromagnetic transition at 0.60 K, which was confirmed by the magnetic entropy of ln2 due to one unpaired electron on the radical molecule and the hysteresis curve. The \ensuremath{\gamma} phase, on the other hand, revealed an antiferromagnetic transition at 0.65 K and one-dimensional ferromagnetic fluctuations above it. The specific-heat data of the \ensuremath{\gamma} phase in external fields were analyzed by a mean-field theory incorporated in the one-dimensional Heisenberg model. The details of sample characterization of each phase based on thermal analysis are also given.

Discovery of a quasi-1D organic ferromagnet, p-NPNN.

Abstract: We discovered that an organic radical crystal, p-nitrophenyl nitronyl nitroxide (p-NPNN), is a quasi-1D ferromagnet induced by unpaired electrons on radicals. The magnetization and the susceptibility of the triclinic γ-phase crystal are very well represented by the Bethe-ansatz solution of the S=1/2 1D Heisenberg ferromagnet with nearest-neighbor coupling J⇒4.3 K. Low-temperature specific heat and ac susceptibility measurements revealed that the crystal undergoes a ferromagnetic transition at 0.65 K The interchain coupling J' was estimated to be about 0.1 K

Transport property of an organic conductor α-(BEDT-TTF)2I3 under high pressure: Discovery of a novel type of conductor

Abstract: We have found quite a new type of transport phenomenon in an organic crystal α-(BEDT-TTF) 2 I 3 under high pressure. Essentially, it is a semimetal or a narrow gap semiconductor. But, the transport property is peculiar. The conductivity of this the carrier (hole) density and mobility change by a about 6 orders of magnitude. They change in a manner so that the effects just cancel out giving rise to the temperature independent conductivity. At low temperatures, the system is in a state with high mobility (3 ×10 5 cm 2 /V·sec) and low carrier density (5 ×10 15 cm -3 ). This state has been found to be very sensitive to magnetic field. We propose a mechanism for the extremely strong temperature dependence of the carrier density. It is based on the band structure and takes the thermal effect into consideration.

The Halogen Bond

Abstract: The halogen bond occurs when there is evidence of a net attractive interaction between an electrophilic region associated with a halogen atom in a molecular entity and a nucleophilic region in another, or the same, molecular entity. In this fairly extensive review, after a brief history of the interaction, we will provide the reader with a snapshot of where the research on the halogen bond is now, and, perhaps, where it is going. The specific advantages brought up by a design based on the use of the halogen bond will be demonstrated in quite different fields spanning from material sciences to biomolecular recognition and drug design.

A room-temperature organometallic magnet based on Prussian blue

Abstract: THE rational design of molecular compounds that exhibit spontaneous magnetic ordering might enable one to tailor magnetic properties for specific applications in magnetic memory devices1–4. In such materials synthesized previously5–17, however, the underlying weak magnetic interactions are incapable of maintaining ordering at ambient temperatures. One remarkable exception is a compound derived from vanadium and tetracyanoethylene18, but the material is amorphous and fragile, and consequently the molecular interactions responsible for its striking properties are not understood. Here we demonstrate another route to the synthesis of a room-temperature organometallic magnet, in which we combine a hexa-cyanometalate [M(CN)6]q− with a Lewis acid Lp+ If L and M are transition-metal ions, then the orbital interactions in the resulting compound can be described by well understood principles21–24, and it is therefore possible to choose the metals to tune the compound's magnetic properties–in particular, the magnetic ordering (Curie) temperature Tc (refs 21–26). We have synthesized a room-temperature magnetic material (TC = 315 K) that belongs to the Prussian blue family of compounds27 (where M is chromium and L is vanadium), demonstrating that transition-metal hexacyano complexes are promising components for the construction of molecule-based high-Tc magnets.

Halogen Bonding in Supramolecular Chemistry

Abstract: Halogen bonding is the noncovalent interaction where halogen atoms function as electrophilic species. The energetic and geometrical features of the interaction are described along with the atomic characteristics that confer molecules with the specific ability to interact through this interaction. Halogen bonding has an impact on all research fields where the control of intermolecular recognition and self-assembly processes plays a key role. Some principles are presented for crystal engineering based on halogen-bonding interactions. The potential of the interaction is also shown by applications in liquid crystals, magnetic and conducting materials, and biological systems.