Masaki Azuma

Magnetic properties of Sr${\mathrm{Cu}}_{2}$${\mathrm{O}}_{3}$ and ${\mathrm{Sr}}_{2}$${\mathrm{Cu}}_{3}$${\mathrm{O}}_{5}$, containing two-leg and three-leg $S=\frac{1}{2}$ ladders made of antiferromagnetic Cu-O-Cu linear bonds, were investigated. The susceptibility of the two-leg ladder material, Sr${\mathrm{Cu}}_{2}$${\mathrm{O}}_{3}$, is characteristic of thermal excitation from a nonmagnetic ground state with a spin gap of about 420 K, while the susceptibility of ${\mathrm{Sr}}_{2}$${\mathr

The unusual property of negative thermal expansion is of fundamental interest and may be used to fabricate composites with zero or other controlled thermal expansion values. Here we report that colossal negative thermal expansion (defined as linear expansion <-10(-4) K(-1) over a temperature range ~100 K) is accessible in perovskite oxides showing charge-transfer transitions. BiNiO(3) shows a 2.6% volume reduction under pressure due to a Bi/Ni charge transfer that is shifted to ambient pressure

A newly designed ferromagnetic, ferroelectric compound, Bi2NiMnO6, was prepared by high-pressure synthesis at 6 GPa. The crystal structure, as determined by synchrotron X-ray powder diffraction, is a heavily distorted double perovskite with Ni2+ and Mn4+ ions ordered in a rock-salt configuration. The presence of 6s2 lone pairs of Bi3+ ions and the covalent Bi−O bonds give ferroelectric properties with TCE of 485 K, while −Ni2+−O−Mn4+−O−Ni2+− magnetic paths lead to a ferromagnetism with TCM of 14

Magnetic susceptibility and specific heat were measured for a Zn-substituted spin-1/2 Heisenberg two-leg ladder compound Sr(${\mathrm{Cu}}_{1\mathrm{\ensuremath{-}}\mathrm{x}}$${\mathrm{Zn}}_{\mathrm{x}}$${)}_{2}$${\mathrm{O}}_{3}$ (x\ensuremath{\leqslant}0.08) to investigate nonmagnetic impurity effects on the quantum spin system with a large spin gap of about \ensuremath{\sim}400 K. A clear anomaly attributed to the onset of an antiferromagnetic ordering was observed both in the magnetic susce

Patients with head and neck cancer undergoing reconstructive surgery using a prebent reconstruction plate fabricated according to an MRP mandibular model showed improved mandibular contour compared to patients undergoing conventional mandibular reconstruction. Thus, use of this new technology for mandibular reconstruction results in an improved esthetic outcome with the potential for improved quality of life for patients.

The valence state change of BiNiO3 perovskite under pressure has been investigated by a powder neutron diffraction study and electronic-state calculations. At ambient pressure, BiNiO3 has the unusual charge distribution Bi(3+)(0.5)Bi(5+)(0.5)Ni(2+)O3 with ordering of Bi(3+) and Bi(5+)charges on the A sites of a highly distorted perovskite structure. High-pressure neutron diffraction measurements and bond valence sum calculations show that the pressure-induced melting of the charge disproportiona

The crystal structure change of the solid solution BiCo1-xFexO3 was investigated in order to determine the phase boundary between tetragonal BiCoO3 and rhombohedral BiFeO3. It was found that BiCo1-xFexO3 with x = 0 to 0.6 had tetragonal BiCoO3 structures, while those with x = 0.8 to 1 had rhombohedral BiFeO3 structures at room temperature. The monoclinic √2a ×√2a ×a phase was found for the x = 0.7 sample. The tetragonal-to-cubic phase transition was first observed at around 700–850 °C in Bi-base

Bismuth ferrite (BiFeO₃ ) is the most widely studied multiferroic material with robust ferroelectricity and antiferromagnetic ordering at room temperature. One of the possible device applications of this material is one that utilizes the ferroelectric/piezoelectric property itself such as ferroelectric memory components, actuators, and so on. Other applications are more challenging and make full use of its multiferroic property to realize novel spintronics and magnetic memory devices,

Polarization rotation induced by an external electric field in piezoelectric materials such as PbZr_1-_x Ti_x O₃ is generally regarded as the origin of their large piezoelectric responses. Here, the piezoelectric responses of high-quality cobalt-substituted BiFeO₃ epitaxial thin films with monoclinic distortions are systematically examined. It is demonstrated that polarization rotation plays a crucial role in improving the piezoelectric respons