Table of contents

The gamma phase of FeTiD is shown to be monoclinic with space group P2/m and lattice parameters a=c=4.7044+or-0.0012, b=2.8301+or-0.0005 and beta =96.97+or-0.05 degrees . The unit cell contains two formula units and the deuterium atoms are ordered on octahedral interstitial sites.

The effects of the addition of trace amounts (12-96 at PPM) of Sc upon the annealing of otherwise high-purity Cu quenched from 600-700 degrees C has been investigated. The Sc solute was observed to suppress the normal post-quench vacancy annealing in Cu, apparently by the formation of highly stable vacancy-Sc complexes which subsequently annealed only at temperatures in excess of approximately 300 degrees C.

Electronic density of states in amorphous and liquid iron is calculated for the systems of dense random packing model relaxed by means of the Pak-Doyama potential for crystalline alpha iron. The d orbital degeneracy is fully taken into account. An essential difference in the electronic structure is found between amorphous and liquid iron, i.e. the density of states for amorphous iron has double-peaked structure whereas that for liquid iron does not.

The behaviour of the temperature derivative of the electrical resistivity rho near a spin reorientation transition is discussed along a Landau-like theory. The strong diminution of the role of critical fluctuations leads to a sharp break in d rho /dT. Evidence is shown by new results on d rho /dT in polycrystalline gadolinium with very high purity ( Gamma approximately=85).

The first empirical value of a surface scattering phase shift is presented. It is deduced from experimental data of Jaklevic and Lambe, (1975), on tunnelling into size-quantised Pb films. Its value for electrons travelling in the (111) direction with energy e_F+0.8 eV is sigma =(-0.23+or-0.04) pi . This value agrees with an approximate theoretical calculation.

The concentration dependence of the Neel temperature for the dilute Cr-Ga alloy system has been determined by measuring the electrical resistivity and thermal expansivity. By addition of Ga, the Neel temperature decreases at first and then increases abruptly, showing a minimum around 0.7% Ga. This behaviour is very similar to that of the dilute Cr-Al alloy system. The antiferromagnetic spin structure has been presumed to be incommensurate with the lattice below 0.7% Ga from the results of concentration dependence of the Neel temperature and thermal expansion characteristics.

The martensitic HCP-FCC transition in pure Co at T_M approximately 700K exhibits premonitory effects found by purely elastic and by inelastic neutron scattering. Above T/T_M approximately 0.95 preformed cubic nuclei start to grow considerably. At about the same temperature the elastic shear constant c₄₄ decreases sharply. Approaching T_M the entire TA branch corresponding to c₄₄ goes down in energy. No pronounced soft mode behaviour, however, could be found.

Local atomic arrangements were investigated as a model of amorphous iron in terms of Voronoi polyhedra for a dense random packing of hard spheres with and without relaxation. The structure of liquid iron was also simulated in a computer. The amorphous structure was microscopically described as a mosaic of crystalline and noncrystalline polyhedra. The authors have also searched for possible cavities involved in the amorphous structure and found all the Bernal holes. A chain of independent tetragonal dodecahedron (TDs) and trigonal prisms capped with three half-octahedra (TPs), which contact each other on common edges or common faces, could be constructed by trial and error, preferentially retaining the face-contacting holes. If the dislocation model is accepted and the TDs and TPs are regarded as the core structure, the dislocation density is estimated to be 3.4*10¹⁴/cm².

The authors have calculated the interaction energy of two H(He) atoms in Al and Mg using the nonlinear Hohenberg-Kohn-Sham density functional formalism. They study the energy of a pair of H(He) in an otherwise perfect crystal as well as in the neighbourhood of a vacancy. It is found that a dumb-bell arrangement is favoured in which the two H(He) are displaced towards the vacancy from interstitial sites collinear with the vacancy. Qualitatively, the trends found in the results are consistent with experiments on Al samples with large H concentrations, and it is suggested that the inclusion of lattice relaxation within the present model is worth pursuing.

Molybdenum samples of two different impurity levels (one set of a few parts per million and another set of some tens of parts per million concentration) were irradiated at about 60 degrees C with electrons of energies 2, 10, and 40 MeV. Subsequent measurements at 20 degrees C indicated that the average lifetime for positrons trapped in the created vacancies and vacancy clusters increase with irradiation energy from about 190 ps to about 250 ps. It is argued that the former lifetime is due to trapping in monovacancies, whereas the latter results from trapping in a mixture of monovacancies and small vacancy clusters of average size 3-4 vacancies. Rough estimates indicate the concentration of clusters for the 10 and 40 MeV samples to be of the order of 10-50% of the monovacancy concentration.

Neutron inelastic scattering experiments and specific heat experiments have been used to determine the crystal field level scheme in the cubic compound TmCu₅ (AuBe₅ structure). The lowest level is a non-magnetic doublet, lying in energy only slightly below a magnetic triplet level. The crystal field parameters are W=-(0.065+or-0.005) meV and x=0.95+or-0.05.

Measurements have been made of the heat capacity of three electrotransport-purified specimens of neodymium in the temperature range 2-10K and in zero magnetic field. The authors observed more peaks in the heat capacity than have previously been reported, and by comparison of their work with published neutron diffraction data they can draw some conclusions about the magnetic structure of neodymium below 10K.

Andersen (1975) has recently introduced a linear augmented plane wave method (LAPW) for the calculation of electronic structure that was shown to be computationally fast. A more general formulation of an LAPW method is presented here. It makes use of a freely disposable number of eigenfunctions of the radial Schrodinger equation. These eigenfunctions can be selected in a self-consistent way. The present formulation also results in a computationally fast method. It is shown that Andersen's LAPW is obtained in a special limit from this formulation. Self-consistent test calculations for copper show the present method to be remarkably accurate. As an application, scalar-relativistic self-consistent calculations are presented for the band structure of FCC lanthanum.

NMR relaxation times T₁ and T₂ at the Sc and La sites have been measured in a series of intermetallic compounds ScB (B=Cu, Ag, Pd, Rh, Ir, Ru) and LaAg. The product (T₁T) is constant for temperatures between 30K and 300K. Below 30K an influence of magnetic impurities on the susceptibility and spin-lattice relaxation time measurements has been found. The analysis for the electronic structure is given in terms of local susceptibilities based on these T₁ measurements and in terms of a two-band model.

The energy bandstructure of indium has been computed using the relativistic KKRZ method in conjunction with the relativistic modification of the quantum defect method. From the energy band data the Fermi surface of In has been studied in detail. The results predict that the second-zone hole surface is a closed one and that besides the beta arms tiny portions of the third-zone electron surface ( alpha arms) exist around the T point. The band diagrams have further been utilised to calculate the density of states and optical spectra via the joint density of states. The various results obtained agree well with experiments.

Two alloys of the Fe-Si system have been investigated by means of polarised neutron diffraction: a 7.5 at.% Si alloy and a 14.3 at.% Si alloy. The alloy of higher Si content showed some long-range order. For Fe₉₂₅Si₇₅ both the spherical and aspherical form factors were found to be equal within errors to those of pure Fe; for Fe₈₅₇Si₁₄₃ the magnetic moments and form factors were obtained for the three different sites. The Si site was found to have a form factor very different from that of pure Fe. The authors discuss these results and show that they are probably due to the contribution of the electrons at the bottom of 3d band states of Fe atoms when they occupy the Si site.

A method of wide applicability is presented for evaluating the ferromagnetic susceptibility. This leads to expressions for the ferromagnetic threshold in various approximations to the spectral weight function, and it is found that a modified Stoner criterion can always be defined. For the single-band Hubbard model the absence of an instability in the CPA is confirmed, while details are given of the magnetisation to be expected in a twofold degenerate semi-elliptic band.

A Landau-Ginzburg theory for macroscopically inhomogeneous ferromagnetic systems involving only one magnetic species is developed in terms of the local densities of the magnetic atoms. For a nearly homogeneous system the shifts of the Curie temperatures due to the inhomogeneities are discussed. The paramagnetic susceptibility and the spontaneous magnetisation are also considered.

The spin lattice relaxation rate and shift of Cu near-neighbour nuclei of Mn in CuMn dilute alloys have been measured in a wide range of fields (5 kG<H<60 kG) and temperatures (1.4K<or=T<or=250K). For g mu _BH<<k_BT the data show that the Mn electron spin relaxation rate tau ^-1 increases at low T with respect to the limiting high T Korringa rate. The impurity g value can be estimated from the data for g mu _BH/k_BT approximately 1 and is found to decrease at low T. The variations of g and tau ^-1 are shown to be consistent with each other. Theoretical perturbation calculations of the sd exchange model including not only the first ln T term but also the higher-order divergent terms are required to explain these results quantitatively, even for T>>T_K.

The magnetic properties of the Laves phase series Gd(Fe_1-xAl_x)₂ have been studied by means of magnetisation measurements in fields up to 160 kOe for 0<or=x<or=1.0. The Curie temperatures show a rapid decrease with increasing x values, followed by a slight increase for x>or=0.8. The mean magnetic moment increases almost linearly from GdFe₂ to GdAl₂. This implies a constant iron moment for all iron atoms throughout the whole concentration range. The Gd atoms appear to be the magnetising element of the diluted Al-Fe matrix.

The nuclear and magnetic diffuse neutron scattering cross sections at 4.2K of a 4.7 at.% CuMn single crystal have been measured along the (100), (110), and (210) directions using polarisation analysis. The cross sections have been corrected for nuclear spin incoherent scattering by a similar measurement on a natural copper single crystal. The alloy is shown to be atomically random and, assuming g=2, the electronic spin per Mn atom S=1.77+or-0.05. The first-neighbour spin correlation is shown to be ferromagnetic.