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Analysis of the electronic specific heat constant for some Y(Ni,Al)₅, La(Ni,Al)₅, La(Ni,Cu)₅ and Th(Ni,Al)₅ alloys suggests that the amount of hydrogen absorbed in excess of 3 H atoms per RM₅ formula unit (0.5 H atom per metal atom) by the RM₅ phases depends upon the number of unpaired 3d nickel electrons. The so-called 'aluminium anomaly' is also explained on the basis of these results.

The nuclear and magnetic scattering from a 73 at.% gamma -MnNi single crystal has been measured along the (100), (110) and (111) crystal directions using neutron polarisation analysis at 4.2K. The nuclear scattering is consistent with the presence of atomic short-range ordering significant only for the first few neighbours with nickel atoms tending to prefer a manganese-rich atomic environment. The magnetic scattering, due to spatial fluctuations of moments, if analysed using a superposing defect model centred on nickel atoms, indicates a defect radius of approximately 6 AA. The nickel moment is (0.1+or-0.1) mu _B. Along the (100) crystal direction there is an excess contribution to the magnetic diffuse scattering which is thought to be due to static transverse moment fluctuations.

Inelastic neutron scattering measurements have been used to determine the site occupied by hydrogen in alpha Zr-H and alpha and beta Ti-H. The measured optical peak frequencies were only consistent with hydrogen being located on the tetrahedral sites in all cases. The significance of the energy shift between the hydride phase and the solid-solution phase is discussed.

The authors have obtained detailed information on the short-range order (SRO) in Fe_1-cV_c alloys over a large range of concentrations (1<or=c<or=20 at.% V) using neutron diffuse scattering and zero field NMR on the ⁵¹V nuclei. The theoretical and experimental limitations of these complementary techniques are discussed. In the dilute limit (c<or=3 at.%) NMR is more sensitive than neutron scattering in determining the SRO parameters alpha _i whereas beyond a few per cent, neutron scattering is more suitable and gives access to a larger number of alpha _i values. Over the whole range of concentration and temperature investigated, the observed behaviour corresponds to strong repulsive interactions between first or second nearest-neighbour vanadium atom pairs.

The available microscopic and macroscopic dilatometric data were used to calculate the effective defect concentrations, Delta N/N₀, in potassium. Plotted in the Arrhenius diagram all these concentrations exhibit a concave ('negative') curvature, opposite to that found for example, for the diffusion coefficient. If the data are trusted the observed behaviour indicates the presence of a complicated defect system in potassium consisting of both vacancies and interstitials. Otherwise, either the microscopic neutron diffraction lattice parameter data or the macroscopic dilatometric results (or both) must contain large systematic errors.

By means of the diffusion broadening of the Mossbauer resonance and of a new technique of positron lifetime measurements, point defects in the vanadium refractory metal have been investigated up to the melting point. Values of formation and migration enthalpies and entropies have been obtained for both monovacancies and divacancies: H_1V^F=(2.2+or-0.4) eV, H_2V^F=(3.7+or-0.8) eV, S_1V^F=(4.8+or-1.4)k_B, S_2V^F=(11.0+or-1.4)k_B, H_1V^M=(1.2+or-0.3) eV, H_2V^M=(0.8+or-0.3) eV.

Using a local Heine-Abarenkov model potential and the perturbational formalism, the elastic shear constants C₄₄ and C'=(C₁₁-C₁₂)/2 of alkali metals subject to pressure are derived theoretically, and the pressure derivatives of the elastic stiffness constants dB/dP, dC₄₄/dP and dC'/dP arising from volume changes are calculated. The values of the elastic constants increase with increasing pressure, and those of the pressure derivatives dC₄₄/dP and dC'/dP decrease with increasing pressure.

Temperature-dependent radio-frequency size effect data have been obtained for many orbits on the Fermi surface of antimony. These data are analysed according to a model in which the electron-phonon scattering frequencies are proportional to T³, but because of a low effective Debye temperature for the small pieces of Fermi surface, the logarithm of the amplitudes of the data is proportional to T². The electron-phonon scattering frequencies are determined for both holes and electrons and are found to be highly anisotropic in each case.

Neutron scattering experiments have been performed in order to measure the position of the optic phonon modes in hydrogenated and deuterated alpha phase Ti and Zr. The weak anharmonic effects are discussed with respect to the superconducting properties of these materials, especially the observed inverse isotope effect in Zr-(H, D). It is shown that the superconducting behaviour of both Ti-(H, D) and Zr-(H, D) cannot simply be correlated with the position of the optic phonon modes.

The conduction electrons of an alloy contribute to the thermotransport through driving forces due to (i) their unsymmetrical momentum distribution in a thermal gradient, (ii) the internal thermoelectric field and (iii) the density dependence of the interionic forces mediated by the electron gas. Proceeding from general linear response theory, the author obtains practicable expressions, valid at all concentrations, for the driving force on a given ion in terms of the contribution of this ion to the thermoelectric power. The response of the ions to the forces is also considered and it is shown that in a liquid binary alloy their contribution to the concentration gradient is proportional to S_cc, the concentration-concentration structure factor.

Using density functional theory the electronic structure of 4d transition metal and sp impurities from the third, fourth and fifth rows of the periodic system in a Cu matrix is calculated self-consistently. The authors use the local spin density approximation of Hedin and Lundqvist. The impurity is embedded in the perfect crystal environment and described by a single perturbed muffin-tin potential in the KKR-Green function scheme used previously for other impurities in Cu, Ag and Al. Results are given for the local density of states, scattering phase shifts, local charges, change of density of states at the Fermi level and residual resistivity. The density of states of the virtual bound states of 4d impurities is not very Lorentzian-shaped due to a rather large d-d interaction and the local density of states at the bottom of the Cu d band is more similar to pure Cu than it was for 3d impurities. The sp impurities are electronically characterised by a piling up of s or p bonding and antibonding states at both sides of the Cu d energy region gradually shifting to lower energies when they are filled.

The authors develop a method for the band calculation of muffin-tin alloys which is as simple as the Korringa-Kohn-Rostoker (KKR) method for pure crystals. They begin by postulating Bloch-like basis functions, minimise the energy and arrive at a secular matrix with a formal resemblance to the secular matrix of the average t-matrix approximation (ATA) method. The density of energy states is derived from an argument based on the number of orthogonal basis functions. Using a similar argument, they derive an expression for the energy variance of the Bloch-like states. The advantage of the method is its extreme simplicity: an alloy calculation actually becomes as simple as a band structure calculation for a pure crystal. The method is also extended to situations in which it is feasible to increase the precision of the calculation by working with unit cells with more than one atomic site. Finally, the method is applied to a unidimensional alloy and compared favourably to a CPA and to a Monte Carlo calculation.

On the basis of the local density functional approximation the authors re-derive a local force theorem and, from this, a linearised expression for total energy differences. This can be used to decompose calculated heats of formation into angular momentum contributions constituting a basis for a bond analysis of heats of formation. They demonstrate this by applying the linearised theory to analyse results of augmented spherical wave calculations of the electronic structure and heats of formation of the transition-metal hydrides NiH, PdH, IrH, PtH and AuH.

The electrical resistivity in the temperature range up to room temperature for the Gd_1-xEr_xAl₂ system has been investigated. The Curie temperature, T_c, spin-disorder resistivity, rho _s, and residual resistivity, rho _r, were determined. Anomalous behaviour of the spin-disorder resistivity versus Er concentration and correlation with the X-ray structural disordering investigations has been observed.

The longitudinal magnetoresistance of a Pd-0.15 at.% Mn alloy has been measured in various fixed fields between 1.5 and 10K. Within experimental error the magnetic scattering component can be expressed as a unique function of H/T over the entire field and temperature range examined. These data are well fitted using an expression calculated from a simple s-d model in the first Born approximation provided an enhanced (but well defined) value for both the g factor (g_eff=2.44) and the effective spin (S_eff=3.0(2)) are used. These fitting parameters are consistent with other data. An enhancement of the g factor via the local moment-d band exchange coupling yields a value of g_eff=2.22, somewhat less than that found experimentally.

Considerable evidence indicates that in Fe above the Curie temperature the electron system forms local magnetic moments which are relatively stable in magnitude and rotate to destroy long-range order. The local moments arise from exchange polarisation of the electron gas in a similar way to the conventional picture of the ferromagnetic ground state of the metal. The authors set up a one-electron-like Hartree-Fock-like model with a Stoner-like intra-atomic exchange interaction for calculating the electronic structure of such a system with arbitrary directions for the atomic moments. The directions for a cluster of 500-1000 atoms are assumed and fed into the calculation, from which the magnitudes of the moments are computed self-consistently using Haydock's recursion method (1980). The total energies are also obtainable. Results are presented for two simple types of magnetic configuration: spin spirals represent a smooth variation of the direction of magnetisation whereas alternating tilts form a rough variation back and forth from atom to atom.

For pt.I see ibid., vol.12, no.1, p.177 (1982). A previously described mathematical technique is applied to the excited states of ferromagnetic iron. The calculations considering only the d band are used although a preliminary calculation involving an s band is included. This shows that no qualitative differences appear although values of the local moment m and spin-wave stiffness D are brought into better quantitative agreement with experiment. It is shown that the local environment (largely the nearest neighbours) of perturbed spins dominates the excitation energy, and that this energy is higher if the local order is 'rough' ( Del ²m=0) than if it is 'smooth' ( Del ²m=0). Two easily calculable excitations, the spin spiral and alternating tilt, are shown to be broadly representative of the high-energy excitations. A set of Heisenberg J are calculated and give a reasonable mean field value for T_C. Finally, spin-wave dispersion curves are calculated both at low q from the spin spirals, and over a wide range of q from the Heisenberg J. The low-q stiffness was found to be in good agreement with experiment when both s and d bands were used, but was somewhat lower in the calculations with only d bands.

Experimentally observed intensity variations in Bragg peaks, which arise from magnetic neutron scattering, indicate that 180° magnetisation reversals dominate the magnetisation processes in low applied magnetic fields. Whereas such reversals can be associated with 180° Bloch wall motion in multi-domain samples of the ferrimagnet magnetite, Fe₃O₄, a different mechanism seems to be required for milled magnetite, for which 'hysteresis' in its magnetisation is usually attributed to the presence of mono-domain particles. For the milled material, low-field 180° reversals appear to arise from an incoherent process, such as 'curling' or 'buckling' of the magnetisation, rather than from coherent rotation of the moments in unison within uniaxial mono-domain particles. It appears that about half the moment could be incoherently misaligned throughout this reversal process, in zero, as well as in small applied magnetic fields.

Neutron diffraction ( lambda =0.504 AA) has been used to show that below T_N=27+or-3K, GdBe₁₃ exhibits a spiral structure. The propagation vector is parallel to c and independent of temperature. The magnetic moments M of the Gd³⁺ ions are perpendicular to the c axis. The thermal variation of M can be accounted for by means of a molecular field approximation (J=7/2, g_J=2).