Table of contents

Neutron diffraction measurements up to 43 kbar at 298K show that the volume of FCC Cs is smaller than expected from a comparison with the BCC phase, with other alkali metals at high pressure and with transition metals. This is attributed to a continuous s-d transition of the conduction electron character which causes a lowering of the average kinetic energy of the conduction electrons.

It is shown that the Mahan-Nozieres-de Dominicis (MND) theory of X-ray edges (1967-1969) predicts enhanced K edges for all free-electron metals. The K absorption and emission edges of Li and Al overlap, strongly suggesting that the primary source of K edge rounding is core-hole broadening rather than the MND orthogonality catastrophe effect.

The nuclear quadrupole interaction of the 247 keV level of ¹¹¹Cd in polycrystalline metallic zinc has been determined as a function of the temperature by the method of perturbed angular correlations. The temperature dependence is found to be anomalous as in the case of ¹¹¹Cd in cadmium, indicating the close similarity of the nature of the quadrupole effects in these two metals.

Observation of the de Haas-van Alphen effect in a single crystal of yttrium (resistance ratio 120) which was refined by solid-state electrotransport processing is reported. At the c axis two frequencies (3.27*10⁶ G and 3.9*10⁶ G) were observed. The first, for which the cyclotron mass was found to be 0.39+or-0.01 m₀, is interpreted as the orbit delta of Loucks' APW model (1966). The second can also be explained on this model by the introduction of spin-orbit coupling.

The effect of a carbon impurity on the low-temperature magnetic, electric and thermal properties of FCC Ni_1-eFe_c alloys (0<or=C<or=0.65) has been investigated with special emphasis on the higher iron concentration range. The results are as a whole in good agreement with a transition from strong to weak ferromagnetism at the vicinity of the equiatomic composition, and with a strong perturbation of the 'd' states of the matrix by the valence electrons of carbon.

The thermal conductivities of two samples of nominal 75% Nb-25% Zr alloy have been measured below 20K. The measured conductivities are substantially higher than found previously for segregated niobium-zirconium alloys, and the phonon carrier component is found to be completely dominant at all temperatures. The effective number of electrons scattering the phonons is unusually small.

The temperature dependence of the AC susceptibility and the coercive field of gadolinium has been studied near the Curie temperature.

The concept of the anisotropic relaxation time is critically examined. It is shown that an anisotropic relaxation time can be defined in a rigorous mathematical way with no approximation. This anisotropic relaxation time is related to the relaxation of the electronic distribution toward equilibrium at the moment all applied fields are turned off. The anisotropic relaxation time is not to be interpreted as a true time constant for exponential decay of the electronic distribution, but is instead a weighted average of the true characteristic time constants for the electron system. It is pointed out that two conflicting definitions of the anisotropic relaxation time are currently in use and that this has generated some confusion and inconsistency in the literature.

A one electron model is presented for the study of the impurity screening in a normal metal. The conduction electrons of the matrix are assumed to be free. Inner and diffusion impurity states are obtained simultaneously in the Hartree selfconsistent approximation. This model, applied to the dilute AlMg alloy, gives on the whole satisfactory results given the approximation made for the electronic structure of the metal.

The Gibbs-Bogoliubov inequality is used to calculate approximate hard sphere structure factors for liquid metals. The two essential assumptions are (i) second order pseudopotential perturbation theory is valid and (ii) the hard sphere structure factors are adequately described by the Percus-Yevick theory. The results, obtained for many simple metals and for varying conditions of temperature and pressure, are encouraging.

The electrical resistivity of a number of Pd-Rh, Pd-Ru, and Pd-Ag alloys has been measured from about 1K to room temperature, and, in two specimens of Pd-Pt, at temperatures below about 12K. Shallow resistance minima are observed between about 3K and 7K in several of the Pd-Rh alloys as well as in Pd-0.5% Ru and Pd-43% Pt. These minima are attributed to a temperature dependent decrease of the impurity (residual) resistivity, due to a reduction in s-d scattering with increasing temperature, rather than to any form of magnetic scattering. It is also found that all alloys exhibiting resistance minima show rather large negative deviations from Matthiessen's rule above about 100K. Arguments are put forward showing that these originate in the same mechanism as gives rise to the resistance minima. At intermediate temperatures of about 50K, positive deviations are observed in all specimens similar to those found in alloys based on noble metals.

The integrated voltages observed across an open single layer superconducting coil when its magnetization is thermally destroyed by rapid heating at the inner (or outer) surface depend on (i) the initial temperature, (ii) the applied magnetic field and (iii) the diamagnetic, paramagnetic or hybrid nature of the initial magnetization. The signals normalized to the initial magnetic moments, are also seen to increase as the initial moment decreases with all the curves approaching a common extremum value in the limit of infinitesimal moment. By exploiting critical state concepts together with the viewpoint that the observed voltages are produced only by the change of magnetic flux embraced by the measuring circuit excluding the volume of the superconductor all observations are explained.

The magnetic properties of Co_cGa near the critical composition (C_cr approximately=1) are studied in relation to the atomic arrangement of cobalt atoms on gallium and cobalt sublattices obtained from X-ray, and density measurements. From magnetization data (4K<T<300K; 0 kOe<H<50 kOe) it is shown that the paramagnetic-ferromagnetic transition occurs in an inhomogeneous way from isolated pairs (n=2) triplets (n=3) and clusters of n>or=4 cobalt atoms which are nearest neighbours on gallium sites. The magnetization curves Mn(H/T) the magnetic moments and the concentrations x_n of each of these clusters are determined from the concentration dependence of the measured magnetization curves. For quenched samples, the concentrations x_n are consistent with a complete disordered arrangement of cobalt atoms on gallium sites; for slowly cooled samples, the small values for these concentrations x_n suggest that these samples are partially spatially ordered.

The effect of anisotropy produced by heavy impurities in a dilute magnetic alloy on the exchange narrowed and bottlenecked ESR linewidth is considered. For a small heavy impurity concentration an exact treatment is shown to be possible by establishing and solving the susceptibility equations for the system in the anisotropy Hamiltonian representation. The result, when compared with experimental data of Cottet (1971), gives a new estimate for the magnitude of the anisotropy occurring in CuMn+Pt alloy.

Measurements of magnetization and microwave resonance have been carried out on six single crystal gadolinium-yttrium alloys, having compositions 6, 28, 53, 58, 59, and 64 at% gadolinium. From measurements in the temperature range 4K to 290K, values of the exchange parameters J(Q), J(0), J_fs have been estimated. A microwave resonance in the low temperature antiferromagnetic spiral phase has been observed for the 6 at% and 28 at% Gd alloys. Anisotropy constants have been derived from the microwave measurements in the ferromagnetic phases. The order of magnitude of K₂ at 0K is 3*10⁶ erg cm^-3, and the hard axis of magnetization is the (0001)-c crystal axis.

Presents measurements of NMR spin lattice relaxation time in beryllium metal between 300 and 1200K. A very low electronic contribution to the relaxation (T_1e T=1.85*10⁴sK) allows observation of the dipolar contribution due to Be atomic motions as well as the quadrupolar contribution due to field gradient fluctuations coming from vacancy and impurity motions. From the slope of the dipolar contribution, one can deduce a value of 1.35 eV for the self diffusion activation energy in agreement with previous values obtained by T₂ measurements. The quadrupolar contribution attributed to vacancy motions presents a maximum at about 570K. This gives a value of 0.65 eV for the migration energy. The slope of this contribution is strongly dependent on the thermal treatment and the purity of the samples. This can be understood if one takes account of bounded vacancies with binding energy as high as -0.5 eV.

Measurements of the hyperfine interactions at impurity ¹¹⁹Sn nuclei in iron have been made at temperatures between 4.2K and 972K using Mossbauer spectroscopy. Both the hyperfine field and isomer shift measurements, when converted to constant volume, show unusual temperature dependences and it is deduced that these results imply a temperature dependence of the electronic structure in the vicinity of the impurity. Current models for the origin of the hyperfine field at tin and similar impurities in magnetic transition metals are reviewed, and used as a basis for this conclusion. The temperature dependence of the Mossbauer absorption was also measured, and indicates that the tin impurity ion vibrates as an isotopic impurity in the iron matrix.