Spin-polarized LMTO Research Articles

Electrical resistivity of DyCo 3B 2 compound

New results of the transport and electronic properties of DyCo 3B 2 compound are reported. This compound crystallizes in the hexagonal CeCo 3B 2 type structure. The resistivity at low temperatures shows a T 2 dependence, implying that the electron-spin wave scattering is dominant in this temperature range. The experimental results are discussed on the basis of s–d scattering in the high temperature range. The electronic structure of DyCo 3B 2 compound is calculated by self-consistent spin-polarised LMTO method. The calculated contribution from the band structure to the resistivity is close to the experimental results.

On the valence hyperfine field of atoms in face-centred cubic iron and nickel containing 2p interstitials

The valence hyperfine fields of atoms in fcc iron and nickel containing 2p interstitials X ( X = B, C, N, O and F) have been investigated by applying the spin-polarized LMTO method. The results on the valence hyperfine field and the hyperfine coupling constants indicate that the Fe-Fe and Ni-Ni interactions are sensitively dependent on which interstitial atom is present, and also that Fe-X interactions dominated by bonding states are distinguishable from those between Ni and X atoms which `prefer' anti-bonding states. The volume (distance) dependences of the valence hyperfine fields in Fe-X are also investigated, and the results reveal an anomalous distance dependence of the three hyperfine coupling constants. It is concluded that it is the unusual distance dependence of the strong interactions between face-centred Fe and X atoms that gives rise to these anomalies.

Electron-transport properties and electronic structure of the Nd 3Co 11B 4 compound

New results of the electronic and transport (electrical resistivity) properties of Nd 3Co 11B 4 compound are reported. This compound crystallises in the hexagonal Ce 3Co 11B 4-type structure. The magnetisation measurements have shown that the Nd 3Co 11B 4 compound is ferromagnetic with T c = 392 K and saturation moment M s = 12.20 μ B/ f. u. at T = 4.2 K. The electrical resistivity of Nd 3Co 11B 4 compound was measured over temperature range 4.2–360 K. At low temperatures, the resistivity ρ increases with temperatures as T 2, implying that the electron-spin wave scattering is dominant in this temperature range. The experimental results are discussed on the basis of s-d scattering in the high-temperature range. The electronic structure of Nd 3Co 11B 4 compound is calculated by self-consistent spin-polarised LMTO method. The calculated contribution from the band structure to the resistivity is close to the experimental ones.

Exchange Coupling and Magnetization Profiles of Binary and Ternary Magnetic Multilayers

Within a spin-polarized LMTO approach in the Atomic-Sphere approximation we calculate ab initio the magnetic properties of various binary and ternary multilayers composed of Fe, Co, Ni, Cr, V and Cu. The emphasis lies on the indirect exchange interaction of the magnetic sandwiches across the antiferromagnetic or non-magnetic spacers, and on the profiles of the intrinsic resp. induced magnetic moments. Among other results we find: (i) that Ni is very sensitive on its neighborhood and that (ii) at the interface to Fe, V gets almost as strongly polarized as Cr, whereas in the interiour layers, the V sandwich remains nonpolarized.

Magnetic properties of partially ordered Co2−xPdxTiSn alloys

We have studied the influence of the local environment on the electronic structure and magnetic moments in partially ordered Co2−xPdxTiSn alloys. The electronic structure was calculated by the spin-polarised LMTO method for a supercell of 16 simple cubic sublattices. We present the changes in the total density of states with increasing concentrations of palladium in Co2−xPdxTiSn alloys. We did not observe the magnetic moments in ordered CoPdTiSn alloy.

Spectroscopic and magnetic properties of Gadolinium Laves-phase compounds

X-ray photoemission spectra (XPS) and magnetic susceptibility of a series of isostructural Laves-phase alloys Gd(Al 1- x M x ) 2 for M = Si, Cu, Pd, Ag, In, Pb, Sn, Ge, Sb, Ga ( x <- 0.3) were experimentally investigated. The experimental data are compared with the results of ab-initio electronic structure calculations using the selfconsistent scalar-relativistic spin-polarized LMTO method for dopand concentrations x = 0 and x = 0.25. As compared to the experimental XPS spectra, calculated f-peaks of Gd are shifted significantly toward the Fermi level E F . Energetic positions of dopand d-peaks near E F are better reproduced. The experimentally observed decrease of the paramagnetic Curie temperature θ p for increasing dopand concentration x can be explained by a decrease of the density of states (DOS) at the Fermi level E F .

Effect of boron, carbon, phosphorus and sulphur on intergranular cohesion in iron

Spin-polarized LMTO calculations were performed on a simplified model of a (111) Σ3 tilt grain boundary (GB) in bcc Fe. The GB was modelled by a hexagonal 8-atom supercell containing an impurity atom (B, C, P or S) in the center of a capped trigonal prism of Fe atoms at the GB core. It was found that the bonding of atoms in the GB plane is enhanced due to strong hybridization between electrons of Fe and the impurity. Across the GB the bonding is rather strong for B and C, while it is dramatically weakened for P and S, with d-electrons of Fe occupying almost entirely nonbonding states. The magnetic moments of Fe atoms in the GB were found to decrease with respect to those in the bulk, while the magnetic moments of Fe atom pairs across the GB were enhanced. Our results should be important for understanding the GB embrittlement in Fe and Fe-base systems.

Band structures of Ni3Pt and NiPt3

The results of self-consistent, spin-polarized LMTO band structure calculations are shown for the compounds Ni3Pt and NiPt3, ofL12 (Cu3Au) structure. Lattice constants are reported together with bulk moduli, and the electronic structure is studied in relation to magnetism in both cubic compounds. Covalent magnetism is shown to act against the magnetization in Ni3Pt.

Electronic structure of actinide hydrides

We report self-consistent LMTO, spin-polarized LMTO, and RLMTO energy band calculations for ThH 2 and PuH 2 in which the zero temperature equations of state were calculated. For ThH 2 the calculated lattice constant, bulk modulus and cohesive energies are 5.397 Å, 99 GPa and 342 kcal/mol, respectively. For PuH 2 the calculated lattice parameters were 4.74 Å (LMTO), 4.89 Å (RLMTO), 4.98 Å (spin-polarized LMTO) compared with a measured value of 5.395 Å. It is deduced that the 5f electrons in PuH 2 are localized.

Electronic structure of NaCl-type compounds of the light actinides. III. The actinide nitride series

For pt.II see ibid., vol.14, p.653 (1984). The trend in the lattice parameters of the actinide nitride series is interpreted in terms of metallic 5f-5f and covalent cation 5f-anion 2p contributions to the calculated equations of state. The lattice parameters are obtained from self-consistent LMTO, RLMTO and spin-polarised LMTO calculations. Particularly large magnetovolume effects were found for NpN-AmN. Spin-orbit splitting also increased the calculated volumes of NpN-AmN and the density of states at the Fermi level was found to be predominantly of 5f5/2 character for the paramagnetic ground states of UN-AmN.

Magnetism of metallic superlattices

Artificially made layered materials such as modulated structures have added a new dimension to magnetism research. Important parameters are modulation amplitudes and wavelengths, concentration, interface matching, and orientation of the modulation. We have studied theoretically the electronic structure and magnetic properties of various coherent modulated structures by means of self-consistent spin-polarized LMTO band calculations using large supercells to describe the structure. For CuNi, modulations along [111] and [100] were studied for different assumed wavelengths and supercells. In all cases, the calculated Ni moments are found to be reduced compared to fcc Ni. Adjacent Cu layers acquire small moments of varying direction and strength, indicating that the Cu and the wavelength as well as the s-electron moments might be important to mediate the coupling between separated Ni layers. To study effects of local distortions, such as shear and stretching, the magnetic moment in bulk Ni and magnetic susceptibility in Pd have been calculated for tetragonally distorted lattices.

Electronic structure and itinerant magnetism in ZrZn2 and TiBe2

The electronic and magnetic structure of the Cl5 compounds ZrZn2 and TiBe2 has been determined by means of self-consistent spin-polarized LMTO band calculations. The spin-densities and neutron magnetic form factors are compared with neutron scattering data for ZrZn1.9 and TiBe1.8Cu0.2. The moments are found to reside almost entirely on the Zr/Ti atoms, and are found to be 0.14 and 0.21 μB per formula unit respectively.