Tungsten carbide has been shown to be an effective catalyst for a number of reactions that are readily catalyzed by platinum, but not at all tungsten, and it was speculated this behavior is due changes in the electron distribution when carbon added tungsten. A test hypothesis, made measuring valence band x-ray photoelectron spectrum tungsten comparing with spectra shows that, near Fermi level, electronic density states more nearly resembles platinum than

An electronegativity scale is derived for the noble and transition metals, based on their electron-band theory description. The tendency of $d$-band electron hole states to hybridize used estimate propensity a particular metal gain or lose $d$-electron count this, in turn, provide basis scale. Overall agreement this with Miedema's Pauling's remarkably good, granted widely divergent bases three scales. results, combined an average vacancy count, are then structural maps...

Magnetization measurements are reported on a nearly cubic single crystal ${\mathrm{YBa}}_{2}$${\mathrm{Cu}}_{3}$${\mathrm{O}}_{6+\mathrm{x}}$ which displays predominantly one variant of twin boundary. With this crystal, we were able to compare the effects different vortex and twin-boundary orientations magnetic behavior. The results demonstrate that there is measurable effect due direct pinning vortices by boundaries for applied fields perpendicular c axis. We also show large anisotropy in...

A laser-ablation technique was used to deposit thin films from the bulk oxides ${\mathrm{La}}_{1.85}{\mathrm{Sr}}_{0.15}\mathrm{Cu}{\mathrm{O}}_{4\ensuremath{-}\ensuremath{\delta}}$ and ${\mathrm{Ba}}_{2}\mathrm{Y}{\mathrm{Cu}}_{3}{\mathrm{O}}_{7\ensuremath{-}\ensuremath{\delta}}$, whose superconductivity properties were investigated by dc resistivity, complex ac susceptibility, microwave response. The latter employed establish that have superconducting regions with similar materials.

The Knight shift, K , measures the magnetic hyperfine field at nucleus produced by conduction electrons which are polarized in a field. shifts often dominated Pauli term and, its most simple form, can be written as K=〈a〉χp . Here χ p is electron spin susceptibility depends on density of states Fermi level, N(Ef ), and 〈a〉 an average coupling constant associated with wave function character nucleus, ∣ψF (0)∣2, for surface. shift therefore provides, through 〈a〉, insight into wave-function N(EF...

The hyperfine magnetic fields and quadrupole interactions in ${\mathrm{Fe}}_{2}$B ${\mathrm{Fe}}_{2}$Zr are explored by nuclear resonance the M\"ossbauer effect. anisotropy found spectra can be interpreted as a superposition of patterns arising from an anisotropic field electric gradient combination with either two magnetically inequivalent Fe sites (such was observed ${\mathrm{Fe}}_{2}$Zr) or two-dimensional distribution magnetization directions. Assuming former, to...

In a classic paper, Solomon showed that the presence of inhomogeneous, first-order quadrupolar interactions leads to formation extra "allowed" spin echoes in nuclei for which $I=\frac{5}{2}$. We demonstrate (both theoretically and experimentally) shifting rf phase second pulse by 90\ifmmode^\circ\else\textdegree\fi{} (in spin-$\frac{5}{2}$ system) enhances allowed factor almost 5 amplitude over unshifted case. Using density-matrix formulation (and assuming no magnetic inhomogeneities), we...

The nuclear magnetic resonance of ${\mathrm{Ni}}^{61}$ has been studied in pure nickel powders. Both natural (1.25% abundant ${\mathrm{Ni}}^{61}$) and enriched (99.9% were used. signal observed with a circuit sensitive to the absorption power is combination dispersion modes. amount mode mixing found depend on applied rf field, ambient temperature, annealing external magnetic-field intensity. related electronic losses sample. saturation behavior individual modes that an inhomogeneously...

We report a newly observed phenomenon, namely, the observation of visible anomaly in Bloch T(3/2) law for temperature dependence magnetization nanostructured ferromagnets, which we give thermodynamic explanation. Our interpretation extends by introducing system's chemical potential and assumes finite Bose-Einstein condensation T(BE) magnons. extension involves accounting possibility magnon or magnetic entropy term, leading to (hitherto omitted traditional derivation) varies with temperature....

Homogeneous gelled composites of iron and silica containing 11–40 wt. % Fe have been prepared by low-temperature polymerization aqueous solutions ferric nitrate, tetraethoxysilane, ethanol (with an HF catalyst). X-ray diffraction, electron microscopy, Mössbauer effect, magnetization measurements used to show that these bulk materials are paramagnetic at room temperature remain in state 10 K. In this condition the is present nanometer-sized regions exists ionic form (both Fe3+ Fe2+ ). It...

This Letter proposes a scheme for obtaining the $d$-electron energy-band parameters to be used in simple analytic model of alloy heat formation, $\ensuremath{\Delta}H$. The employs, as an intermediate step, equalization local chemical potentials two sites. Calculations $3d$, $4d$, and $5d$ metal alloys yield $\ensuremath{\Delta}H$ accord with experimental trends, but, unlike earlier estimates, $d$ charge transfer direction indicated by experiment.

It is shown that nickel-phosphorus metallic glass alloys not only exhibit two distinct local structural configurations for a given composition, but also the configuration can be selected by choosing appropriate processing parameters. structure exhibiting greater Knight shift exhibits discontinuous transformation to with lower shift. Measurements have been extended amorphous containing up 42 at.% phosphorus.

The metallurgical and electronic structure of TiFeHx alloys are probed by 57Fe Mossbauer effect studies. results qualitatively consistent with support Reilly Wiswall's conclusions (1974) on the phase diagram. Volume effects charge flow both important in isomer shift.