Eiji Hirahara

The Physical Properties of Cuprous Sulfides-Semiconductors

Cuprous sulfide has been observed to have two transition points at about 110°C and 470°C respectively, of which the latter one has been found out experimentally by the writer. The exsistence of the phase transition at 470°C has been confirmed experimentally by the measurements of electronic and ionic conductivity, thermal linear expansion, heat capacity, specific heat and thermo-electromotive force. We, therefore, propose that cuprous sulfide has three polymorphic phases, namely α-phase (above 470°C), β-phase (470°C∼110°C) and γ-phase (below 110°C). In the γ-phase it behaves as a P-type semiconductor (sulphur excess), and its electrical conductivity increases exponentially with temperature. In the β-phase, we have observed the rather remarkable ionic currents together with the sharp decrease of electronic currents. On proceeding to the α-phase, the ionic currents abruptly disappear and electronic currents increase to the larger amount than that in the γ-phase. The transition enery at 110°C has been observ...

The Electrical Conductivity and Isothermal Hall Effect in Cuprous Sulfide, Semi-Conductor

The experimental measurements of the isothermal Hall effect on the γ-cuprous sulfide were performed with the following results. In the stoichiometric specimens, the values of Hall constant R are about (3{sim}4{times}10^{9}left[frac{text{Volt}{cdot}text{cm}}{text{Gauss}{cdot}text{amp}}right]), mobility µ and mean free path l are about 12[cm 2 /Volt·sec], 9[cm], respectively. These values of R , µ and l decrease in the β-phase. As compared with the stoichiometric specimens, the values of µ and l in the sulphur excess specimens do not increase so much as the conductivities do. On the contrary, in the sulphur deficient specimens, the decrease of µ and l is not so remarkable in comparison with that of conductivities. These phenomena may be considered that the impurity scattering due to the free electrons and holes makes the values of µ and l reduce.

Magnetic Properties of Manganese Telluride Single Crystals

The susceptibility and torque measurements of antiferromagnetic manganese telluride are made on the samples of single crystals. The spin orientation and structure are studied and discussed for the observed results of the field dependence and field cooling measurements. Some simple calculations are carried out, and some interpretations for the observed results are obtained on the basis of the assumption of the three-domain structure in the c -planes.

Magnetic field effect on the ultrasonic attenuation in manganese phosphide

Abstract The effect of the external magnetic field on the critical attenuation in MnP near the Curie temperature is observed clearly. The critical attenuation is observed on the boundary of the ferro- and para-magnetic phases, and the temperature dependence of the attenuation peak displays a characteristic behavior along this boundary. Furthermore, a new anomalous peak of attenuation is observed in the paramagnetic phase, and this is the first observation of the attenuation arising separately from each of the three components of the spin correlation function by the ultrasonic technique.

Spin Structure as a Function of Magnetic Field and Temperature in MnP Single Crystal

The b‐axis magnetization has been studied at various temperatures under various values of external magnetic field applied along the b axis, which is the intermediate direction of magnetization. The transformations to the fan structure from the screw and ferromagnetic spin structures have been observed at various temperatures. From these results a spin structure diagram is made as a function of temperature and magnetic field applied along the b axis.

Critical phenomena in antiferromagnetic and paramagnetic resonances near the Néel temperature in europium telluride single crystal

Abstract In the antiferromagnetic and paramagnetic resonances in a single crystal europium telluride, the shift of resonance field from the DPPH-line exhibits a large dip in the vicinity of the Neel temperature, and the resonance line width sharply diverges at the Neel temperature. These phenomena depend on the resonance frequency and the direction of the resonance field.

Antiferromagnetic resonance in Europium telluride single crystal

Abstract Antiferromagnetic resonance in EuTe were observed with 9, 24, and 34 GHz at temperatures 2° and 4.2°K. Mixed signals of two- and sixfold symmetries were observed in the spin-flopped state with rotating field in the (111) plane. By separating the sixfold component we found the easy and hard directions in the (111) plane to be 〈112〉 and 〈110〉, respectively. The amplitude of the sixfold anisotropy field in (111) plane was also determined as H1A = 3.8 ± 1.2 oe at 2°K.

Magnetic Critical Phenomena in MnP by Neutron Scattering

Three‐crystal inelastic neutron scattering measurements have been carried out on a single crystal of MnP in the critical region. The compound is ferromagnetic below its ordering temperature of 291.5°K. The results of the experiments have demonstrated that for T<Tc, there exists a striking dissimilarity between the profiles observed for MnP on one hand and iron and nickel on the other. We have observed for the first time the diffusive fluctuations in a ferromagnet for T<Tc. These results should be contrasted with those that were previously obtained for iron and nickel. For iron and nickel, these diffusive modes have never been clearly observed. The characteristic frequency of the critical fluctuations Γ(κ, ζ) for T=Tc is found to be reliably described by the relation Γ(0, ζ) ∝ζx, where x=2.57±0.11, and ζ is the reduced wave vector. This result is in excellent agreement with the prediction made from dynamic scaling theory. For the isotropic ferromagnet, the dynamic scaling principle predicts a critical expo...