We present measurements of longitudinal ultrasonic velocity on single crystals of the heavy-fermion superconductor UPt3. The measurements show clear signatures of second-order phase transitions in the superconducting state, with the velocity anomalies well accounted for by Ginzburg-Landau theory. From these signatures we construct a phase diagram for UPt 3 that reveals all the boundary lines that have been identified as possible phase transitions. We are able to track the phase transition lines to a tetracritical point, located on the upper-critical-field curve, to within the width of the normalsuperconducting transition.PACS numbers: 74.30. Gn, 62.80.+f, 74.70.Tx This Letter presents the first complete phase diagram in the field-temperature plane for the heavy-fermion superconductor UPt3 derived from a single measurement technique. UPt3 has shown a variety of interesting properties in the superconducting state which strongly suggest unconventional superconductivity with a multicomponent order parameter. Power-law temperature dependences of ultrasonic attenuation 1 " 3 and heat capacity 4 have been interpreted in terms of a gap with line or point nodes on the Fermi surface. More convincingly, a series of experiments have revealed the presence of more than one superconducting phase: Initially, ultrasonic-attenuation measurements showed the presence of two superconducting phases depending on the magnetic field; 5 " 7 subsequently, heat-capacity measurements demonstrated the presence of multiple superconducting phases even in zero field. 8,9 A composite phase diagram assembled from different measurements (ultrasonic-attenuation, 5 heat-capacity, 9 and torsional-oscillator data 10 ) on different samples indicates that UPt3 has at least two and possibly three superconducting phases. However, this interpretation relies on data from a variety of measurement techniques on samples with transition temperatures ranging from 420 to 540 mK.Here we present measurements of ultrasonic velocity on two samples of UPt3. Our velocity measurements yield a more complete phase diagram for superconducting UPt3 than has previously been available. Earlier attenuation measurements on one of the samples 7 (sample No. 1) revealed a peak in the attenuation (the 7/FL peak) in field sweeps at constant temperature, as well as a peak (the X peak) in temperature sweeps in low field. From these attenuation studies it was not possible to follow Hf^(T) very close to the upper-critical-field line HdiT).Thus, it was not possible to answer with confidence the basic question of how many phases there are in UPt3. Theoretical proposals for the phase diagram of UPt 3 have been published by several authors. 11 ' 13 Our results bear directly on these theories:The phase diagrams obtained by a single measuring technique on both of the samples studied give strong support for a tetracritical point intersecting the uppercritical-field line, for fields both parallel and perpendicular to the c axis. In addition, the velocity anomalies at both zero-field transitio...

Thermally evaporated ZnSe thin films deposited on glass substrates within substrate temperatures (T s ) at 303 K-623 K are of polycrystalline nature having f.c.c. zincblende structure. The most preferential orientation is along [111] direction for all deposited films together with other abundant planes [220] and [311]. The lattice parameter, grain size, average internal stress, microstrain, dislocation density and degree of preferred orientation in the film are calculated and correlated with T s .

The peak effect (PE) has been observed in a twinned crystal of YBa 2 Cu 3 O 7−δ for H c in the low field range, close to the zero field superconducting transition temperature (T c (0)) . A sharp depinning transition succeeds the peak temperature T p of the PE. The PE phenomenon broadens and its internal structure smoothens out as the field is increased or decreased beyond the interval between 250 Oe and 1000 Oe. Moreover, the PE could not be observed above 10 kOe and below 20 Oe. The locus of the T p (H) values shows a reentrant characteristic with a nose like feature located at T p (H)/T c (0)≈0.99 and H≈100 Oe (where the FLL constant a 0 ≈penetration depth λ). The upper part of the PE curve (0.5 kOe

The second magnetization peak and the peak effect anomaly coexisting in a given isothermal magnetization hysteresis loop show striking similarities in Ca 3 Rh 4 Sn 13 , a low-T c superconductor and YBa 2 Cu 3 O 7Ϫ␦ , a high-T c superconductor. The observed variation of the hysteresis width with field could imply a modulation in the degree of the plastic deformation of the elastic vortex solid. The characteristics of the high-T c cuprates, such as large Ginzburg number, short coherence length, decoupling of the Josephson coupled pancake vortices, etc., are unlikely to be the cause of the observed behavior.

X-ray diffraction patterns of chemically deposited lead sulphide thin films have been recorded and X-ray line profile analysis studies have been carried out. The lattice parameter, crystallite size, average internal stress and microstrain in the film are calculated and correlated with molarities of the solutions. Both size and strain are found to contribute towards the broadening of X-ray diffraction line. The values of the crystallite size are found to be within the range from 22-33 nm and the values of strain to be within the range from 1⋅0 × 10 -3 -2⋅5 × 10 -3 .

Measurements of the attenuation and velocity of pulsed high-frequency sound have been performed up to 133 MHz in superfluid 3 He-Z?. A new collective mode of the order parameter was discovered at a frequency extrapolated to T c of oo = (1.165 ± 0.05)A K:s (T c ), where ABC S (T) is the energy gap in the weak-coupling BCS theory. The group velocity has been observed to decrease by as much as | of the zero-sound velocity.

Nanocrystalline thin films of CdS are deposited on glass substrates by chemical bath deposition technique using polyvinyl alcohol (PVA) matrix solution. Crystallite sizes of the nanocrystalline films are determined from broadening of X-ray diffraction lines and are found to vary from 5⋅4-10⋅2 nm. The band gap of the nanocrystalline material is determined from the UV spectrograph. The absorption edge is shifted towards the lower wave length side (i.e. blue shift) and are found to be within the range from 2⋅48-2⋅8 eV as grain sizes decrease from 10⋅2-5⋅4 nm. This is also supported by the spectral response curves. An increase of molarity decreases the grain size which in turn increases the band gap.

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