Acoustic experiments on amorphous Pd30Zr70 and Cu30Zr70 in the superconducting and the normal state

Measurements of internal friction and sound velocity of amorphous Pd₃₀Zr₇₀ and Cu₃₀Zr₇₀ around 1 kHz and of Pd₃₀Zr₇₀ around 1 GHz are presented for both the superconducting and the normal state. Our experiments reveal several serious discrepancics with the predictions of the Tunneling Model and its extension to metallic glasses. Particularly from internal friction we conclude that the density of states of the tunneling systems is affected by the presence of conduction electrons. We discuss our results on the basis of recent theories which consider a slowing down of the tunneling motion due to the interaction with conduction electrons.Dedicated to K. Dransfeld on the occasion of his 60th birthday     

μSR study of Cu10Zr7

It is shown that temperature dependences Λ(T) of dipole relaxation rate of the positive muon spin in crystalline and amorphous states of Cu₁₀Zr₇ are approximately the same over the temperature interval 20–300 K. this fact points out approximately identical close-order structure of crystalline and amorphous states of Cu₁₀Zr₇ alloy.     

TDPAC study of amorphous alloys Pd0.8Si0.2 and Pd0.75Si0.20Ag0.05

The amorphous alloys Pd_0.8Si_0.2 and Pd_0.75Si_0.20Ag_0.05 have been studied by the time differential perturbed angular correlation method. A broad EFG distribution with a relative width of 0.48–0.51 was sensed by the probe nuclei¹¹¹Cd for both the amorphous alloys. The unique quadrupole interaction frequencies were observed after annealing above the phase transition temperature. The observed broad distribution of the EFG implies that the crystallographic structure of the amorphous alloys is characterized by short-range order and long-range disorder, which is in accord with the continuous random model.     

Theoretical study of diluted Co/Cu alloys

This study employs the self-consistent Green's function method to study the magnetic properties of diluted _CoxCu1-x${\mathrm{Co}}_x{\mathrm{Cu}}_{1-x}$ alloys from a consideration of their spin dynamics characteristics. The numerical results show that in dilute cobalt concentrations (i.e. x?0.4$x?0.4$), the critical temperatures vary linearly with x for different itinerant carrier concentration conditions. Interestingly, the carrier concentration does not affect the degree of dependency of the temperature on the cobalt concentration when the carrier concentration is less than the atomic number concentration of the alloy.     

Shape magnetostriction in Pd based alloys and in Pd metal

Dilute PdCo and PdNi alloys show strong shape magnetostriction while PdFe shows a much weaker effect, confirming the existence of local orbital moments on Co and Ni atoms in Pd. Comparison with measurements on pure Pd indicates that in Pd metal, the forced shape magnetostriction is mainly associated with the Van Vleck susceptibility.     

Positron annihilation study of order-disorder transformation in Cu alloys

The anomalous change of N₀(T) (the peak counting rates of angular distribution as a function of the temperature of a speciment) due to order-disorder transformation is observed in various Cu-based alloys. The detailed behavior of N₀(T) in AuCu₃ is clearly different from those in CuZn or Cu-Pd alloys, which is attributed to the difference of the order of order-d disorder transformation.     

Photoemission study of Nb-Ni glasses

The photoemission spectra for two Nb-Ni glasses are compared with those for the pure elements Nb and Ni. A decrease in the density of states at the Fermi level is found for glasses as compared with that of either pure element. The significance of this result as related to the formation of the glass is discussed.     

Photoemission study of the Ba core levels in YBa2Cu3O7-x

Angle dependent X-ray photoemission spectra of epitaxial thin YBa₂Cu₃O_7-x films show characteristic differences after various heat and oxygen pretreatments. The component with the lowest binding energy in Ba 3d _5/2 and 4d _5/2 peaks results from bulk Ba in YBa₂Cu₃O_7-x . A component with 2 eV higher binding energy results from Ba in the surface unit cell with different bonding if compared with the bulk superconductor. This surface structure is observed for all YBa₂Cu₃O_7-x surfaces which have been exposed to oxygen. It is not observed for UHV prepared surfaces after mechanical scraping or fracturing.     

Photoemission study of iron-based superconductor

The iron-based superconductivity (IBSC) is a great challenge in correlated system. Angle-resolved photoemission spectroscopy (ARPES) provides electronic structure of the IBSCs, the pairing strength, and the order parameter symmetry. Here, we briefly review the recent progress in IBSCs and focus on the results from ARPES. The ARPES study shows the electronic structure of 122, 111, 11, and 122 families of IBSCs. It has been agreed that the IBSCs are unconventional superconductors in strong coupling region. The order parameter symmetry basically follows s ± form with considerable out-of-plane contribution.     

Photoemission study of Tm metal

A photoemission investigation of Tm metal has been carried out using photon energies in the 100–200 eV range. Electron energy distribution curves and the photon absorption coefficient has been measured and the results are compared to earlier XPS and absorption measurements. No evidence of a valence change at the surface of Tm metal was found, a posibility proposed earlier.     

Photoemission studies of Cu intercalated NbSe2

We report growth and angle resolved photoemission studies of Cu intercalated NbSe₂. Cu_xNbSe₂ with x=0, 0.04 and 0.08 were grown by iodine vapor transport method. Intercalation and doping was confirmed by the change in the c-axis lattice constant and the change in the electronic structure, respectively. To investigate the nesting condition, we performed auto-correlation analysis on the data. We find that the magnitude of the nesting vector decreases with doping but the direction remains unchanged. Our observation is consistent with the nesting coming from intra-pocket transition.     

Photoemission and luminescence properties of quartz glass implanted with Cu+ ions

The special features of optically stimulated electron emission and luminescence of defects in KV quartz glass after Cu⁺ ion pulse implantation are studied. It is shown that the ion-beam modification of the photoemission and luminescence properties of samples is due to the formation of radiation defects and by dimensional factors caused by the appearance of Cu nanoparticles.     

Production and study of metastable state in vapor-quenched Co−Cu alloys

X-ray studies and magnetic measurements on the metal films produced have revealed a number of their structural and magnetic features. Dnepropetrovsk State University. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 11, pp. 24–29, November, 1998.