From sound attenuation measurements, 3 He– 3 He interaction potentials in 3 He– 4 He mixture under 10 and 20 bar have been determined. The measurements were carried out in mixtures of 3 He mole fraction ranging from 0.0289 to 0.0803. Superfluid transition temperatures of 3 He and other properties in the mixtures were then estimated from the deduced interaction potentials. The superfluid transition temperature for s-pairing was found to lower with increasing pressure, whereas a rather high transition temperature, as high as 100 µK, can be expected under 10 bar at the highest soluble 3 He concentration.
The transport critical current density J c of single-crystal YBa 2 Cu 3 O 7-δ thin films has been measured in weak magnetic fields applied at varied angles to the film surface. There are samples with the hysteresis of J c against H and with no hysteresis. The hysteresis occurs in fields not parallel to the direction of the transport current except near the critical temperature. The presence of the hysteresis is related to the value and the temperature dependence of electrical resistivity.
Two acoustic studies in liquid helium recently carried out in the present group are reported. The first of these is the study of critical sound attenuation and dispersion associated with the critical phenomena near the super fluid transition temperature, where the validities of the dynamic scaling hypothesis and the universality precept are claimed. The second one is the study of dynamic properties of normal liquid 3 He, a typical Fermi liquid, by the use of sound attenuation. A Landau parameter F 2 and the lifetime of 3 He quasiparticles have been obtained as functions of pressure.
Sound attenuation peaks around 1 K have been measured at 10, 30 and 50 MHz in 3 He– 4 He mixtures of the 3 He concentration x 3 =0.013, 0.029 and 0.050 under the saturated vapor pressure. The relaxation time related to the interaction between phonons and 3 He quasiparticles has been determined experimentally, and its temperature and 3 He concentration dependences agree with the theory of Khalatnikov and Zharkov.
Li 3 VO 4 - and Li 3 PO 4 -type structure crystals are found as new types of nonlinear optical materials for second-harmonic generation (SHG). Their lattices are formed of only the MO 4 oxygen tetrahedra, being different from other typical nonlinear optical materials that have previously been developed.
The magneto-optical Faraday effect of porous films comprised of cobalt-substituted barium ferrite (Co:BaM) fine particles fixed by a resin was investigated. The films were prepared by spin-on process of a magnetic ink involving Co:BaM particles on glass substrates. Porous films were formed when the particle concentration of the ink, f, was low, i.e., f<0.3, and the coated ink was dried while applying a dc magnetic field normal to the substrate plane. The pit size became bigger when the coated ink was thicker, or the field was stronger. The Faraday effect of the films underwent a drastic change caused by the formation of a porous structure. The Faraday rotation spectrum exhibited dispersion-type behavior and its center wavelength was shifted toward longer wavelength with increasing pit dimension. Rotation angle enhancement was observed, which is considered to be caused by the mode modulation of light due to the existence of the pits.
An apparatus has been designed to control and stabilize temperature in the range 2–20 mK using the adiabatic demagnetization technique. Using a standard CMN demagnetization cell, the temperature of liquid 3 He was stabilized within ±0.5 µK.
