Table of contents

The energy band structure of metallic gold has been calculated by non-relativistic and relativistic augmented plane wave methods. The E(k) against k curves are plotted for some directions of high symmetry. The conduction band is an s-d mixture. The density of states curves are plotted. The results are compared with available experimental and other theoretical data on the band structure of gold

The potential arising from a gold (silver) atom soluted in a silver (gold) metal is determined from observed residual resistivities. Some phenomena in gold-silver alloys are considered by use of this potential. For the nuclear magnetic resonance relating to the electronic density on the Fermi surface at a nuclear position, the present potential leads to good agreement with existing experiments. The nuclear specific heat of the alloy, which results from the interaction between the electric quadrupole moment of ¹⁹⁷Au and the electric field gradient due to the impurity potential, is also considered. It is found that the composition dependence is theoretically given by x_Au²(1−x_Au) in a high temperature range, where x_Au is the atomic fraction of gold atoms in the alloy. From a comparison with experiments the Sternheimer antishielding factor at a gold nucleus is found to be 66

Measurements in the low-energy fine-structure region adjoining the K absorption edge of aluminium have revealed a change in energy position of the pronounced 29 eV absorption minimum on lowering the temperature from 293 to 77 K. This displacement was about three times larger than expected from thermal contraction of the lattice. It is inferred from these observations that at low temperatures a decrease may occur in η(k), the term representing, in the Kozlenkov theory, the effect of the field of the absorbing atom upon the wave of the ejected electron

Using a pulse method, the attenuation of longitudinal ultrasonic waves is measured in nickel and cobalt under different static stresses up to 17 kg wt mm^-2. The measurements are carried out at 20 and 90 °C for the ultrasonic frequencies 2, 3 and 6 MHz in magnetized and nonmagnetized specimens. Attenuation peaks are recorded at certain intermediate stresses independent of the frequency used. However, the position and height of the peaks are found to change with magnetization and temperature variation. This indicates a temperature-sensitive magnetic origin for the peaks observed. An explanation for the origin of such anomalies could be found in the rotation of the direction of spontaneous magnetization inside a magnetic domain, as a result of the applied stress. This view is supported by a calculation of the values of stress at which the attenuation peaks should appear; the calculated and experimental values of stress are found to be in good agreement

The temperature variation of the intensity of the diffuse peak observed near the (100) position in powder neutron diffraction patterns of an equiatomic γ-MnFe alloy and of several Mn-rich γ-MnCu alloys has been measured. The intensity of the diffuse peak reaches a maximum at the Neel points of the alloys which are antiferromagnetic and approaches zero at 4.2 K for equiatomic MnFe but not for the MnCu alloys. The results of both double axis and triple axis neutron diffractometry of paramagnetic and antiferromagnetic alloys suggest that the diffuse peak is mainly due to static or quasistatic short range order. Comparison of the neutron and X-ray patterns of an 82 at.% MnAu alloy showed that less than 10% of the diffuse peak observed in the neutron pattern could be due to atomic short range order. No change was observed in the diffuse (100) peak in the neutron diffraction patterns of a 68 at.% γ-MnCu null matrix alloy after heating, although considerable atomic clustering was revealed

The critical field required to induce this transition in Fe-Rh alloys close to the equiatomic composition has been measured using pulsed magnetic fields up to 280 kOe. Measurements of the thermal expansion and high field magnetization have also been carried out. It is found that application of Kittel's theory of exchange inversion to the results leads to serious numerical discrepancies. A four sublattice model is developed which indicates the importance of the excess entropy of the ferromagnetic over the antiferromagnetic phase in exciting the antiferromagnetic-ferromagnetic transition. The exchange iteration β between iron sublattices is small and negative and, although its lattice parameter dependence is large and positive, there is no suggestion of exchange inversion corresponding to a change in sign of β at the antiferromagnetic-ferromagnetic transition. Thus the ferromagnetic state is stabilized by the excess entropy even in the presence of antiferromagnetic interactions and this stability is maintained right up to the Curie temperature

Measurements have been made on the residual resistivity and the thermopower of various palladium-hydrogen alloys, most of which were in the two phase region. It is found that the variation of the resistivity with either hydrogen or deuterium concentration may be explained on the simple basis that the observed resistivity is an appropriate average between the resistivities of the pure alpha and beta phases. A consistent explanation of the variation of the thermopower can only be found if one includes the effects of supersaturation in the discussion. The thermopower results suggest that hydrogen induced S to d electronic scattering does not play an important role in these alloys, contrary to the case of palladium-silver alloys

A treatment of Anderson's model for dilute alloys of the (orbitally degenerate) 3d transition elements dissolved in simple hosts is given, applicable in the strong-coupling (atomic) limit and at temperatures well above the Kondo temperature. The theory is applied to the impurity susceptibility and resistivity to obtain spectroscopic information on the impurity atom. Experimental magneton numbers from the high temperature susceptibility are used to label the atomic states of the impurity. Residual resistivities are then used to obtain the energy spacing | T − μ | between the virtual bound state T and the Fermi level μ . Given this information, the sign of T − μ is fixed by calculating the magneton number and comparing with experiment. In most cases good agreement can be obtained: the comparison serves as an internal check between theory and observation

Marked discontinuities are observed in the slope of the variation with gold concentration of the ⁵⁷Fe isomer shift, linewidth and hyperfine field in the Mossbauer spectra of palladium gold (iron 2 at.%) alloys at around 50 at.% gold. These are associated with a decrease in the effectiveness of charge screening at the iron sites when the palladium d band is filled. The change from ferromagnetic behaviour in palladium iron alloys to random antiferromagnetic behaviour in gold iron alloys is shown to occur when the d band is filled. The observed Curie temperatures of palladium rich alloys are shown to be determined by the matrix susceptibility. A small change in the slope of the ¹⁹⁷Au isomer shift variation in palladium gold alloys is observed at about 50 at.% gold which was not seen in the earlier experiment of Roberts et al. There is no anomalous behaviour in the linewidth variation, implying little change in the screening of the gold atoms when the d band is filled. Preliminary measurements on palladium copper (iron 1 at.%) alloys indicate a marked discontinuity in the ⁵⁷Fe isomer shift variation at 50 at.% copper

From experiments on a number of Ni based alloys, it is shown that the difference in resistivity for currents perpendicular to and parallel to the magnetization direction is due to spin-orbit induced resistivity transfer from the spin down electron current to the spin up electron current

The effect of pressures up to 1000 bar (10² MN m⁻²) and temperatures up to 1300 K on the thermoelectric power S of liquid mercury and dilute mercury-indium alloys was investigated experimentally for the first time and values of (∂S/∂V)_T and related quantities are given. (∂S/∂V)_T was also measured for the first time in the liquid alkali metals caesium, rubidium, and potassium at temperatures just above the melting point. For the alkali metals there is qualitative agreement with the nearly free electron theory of electron transport in liquid metals. For mercury and mercury indium there is agreement in part and this situation is discussed