Knight shift in superconducting vanadium

The Knight shift in metallic vanadium in the normal and superconducting states has been measured. In contrast to the previously obtained results, this shift appears to change after the transition to the superconducting state. The behavior of the Knight shift in the superconducting state in vanadium samples doped with iron impurities has been found to be different from that in the “pure” samples. As a possible explanation of the effect, the broadening of the peak of the density of states near the Fermi level due to the scattering of conduction electrons on the iron impurities and the earlier predicted impurity polarization shift of the NMR line are discussed.     

Muon Knight shift in palladium

The Knight shift at positive muons implanted in pure palladium has been measured as a function of temperature from 19.8 to 883 K. The Knight shift variation is strictly proportional to the Pd magnetic susceptibility with ΔK^μ/Δ_x=-(0.43±0.02) mole/emu=-(2.39±0.11)kG/μ_B. A temperature independent term K^μ(x=0)=+45±10 ppm is found. The results are discussed in terms of the electronic structure of H in Pd.     

The anomalous Knight shift in beryllium

We calculate the Knight shift (K) in beryllium and magnesium by using the pseudopotential formalism and degenerate perturbation theory. We have included the effects of electron-electron interaction and spin-orbit interaction. We show that K_s, the spin contribution to K, is not linearly related to the spin susceptibility (χ_s) when spin-orbit effects are included. This non-linearity between K_s and χ_s is the origin of the negative Knight shift in beryllium.     

Calculation of the Knight shift in palladium

The direct and the exchange core polarization (ECP) contributions of the conduction electrons to the Knight shift of palladium are evaluated. To obtain the wave functions for the conduction electrons and the partial densities of states at the Fermi surface a KKR energy band calculation was performed. The contributions of the core electrons to the Knight shift were determined by using the moment perturbation method (MP). Electron-electron interactions are taken into account by individual enhancement factors for thed ands electrons. The agreement between the theoretical results and the available experimental data is quite satisfactory.     

Calculation of the Knight shift in palladium

The direct and the exchange core polarization (ECP) contributions of the conduction electrons to the Knight shift of palladium are evaluated. To obtain the wave functions for the conduction electrons and the partial densities of states at the Fermi surface a KKR energy band calculation was performed. The contributions of the core electrons to the Knight shift were determined by using the moment perturbation method (MP). Electron-electron interactions are taken into account by individual enhancement factors for thed ands electrons. The agreement between the theoretical results and the available experimental data is quite satisfactory.     

The Knight shift of francium in mercury

For Fr in Hg an extremely small Knight shift has been found as compared to the shift known for an alkali metal host. It indicates an almost complete loss of the outer s-electron of the alkali atom Fr when embedded in liquid mercury. This may be understood as a consequence of the small ionization energy of the Fr atom in comparison with the large work function of mercury.     

The Knight shift of francium in cesium

Using the PAD technique the Knight shift for Fr in Cs at 273 K has been measured with the 15^– isomer in²¹²Fr. The result 4.9(3)% may be well understood in terms of the conventional analysis. A dominant correction for relativistic effects is the prime source for the extraordinarily large value.     

Isotope effect in the Knight shift of silver

The Knight shifts of the silver isotopes ¹⁰⁷Ag and ¹⁰⁹Ag were determined with high accuracy. Between these shifts there is a difference ΔK = K¹⁰⁷ - K¹⁰⁹ = ?(17.1 ± 1.1) ppm. The relative isotope effect ΔK/K is not in agreement with the hyperfine structure anomaly ¹⁰⁷Δ¹⁰⁹.     

Positive muon Knight shift in graphite and Grafoil

Positive muon Knight shifts and relaxation rates were measured at room temperature in a graphite crystal and in a stack of Grafoil sheets. The Knight shift was 500 ppm in the single crystal and reduced by 0.702 in Grafoil. Both have the same (large) fractional anisotropy relative to the axis or to the normal to the Grafoil sheets, respectively. The (isotropic) relaxation rates were 0.024(4)s^–1 in the crystal and 0.194(6) ^–1 in the Grafoil. Apparently the ⁺ in Grafoil sees highly aligned bulk crystalline graphite, and does not reach the surfaces of the sheets.We are grateful to Greg Dash, the owner of the graphite crystal, for lending it to Tony Arrott; and to Tony for lending it in turn to us.     

Temperature dependence of the Knight shift for cadmium in palladium

The Knight shift and its temperature dependence for a Cd impurity in palladium metal were measured by means of DPAD- and DPAC-methods utilizing the well known 5/2⁺, 247-keV state in¹¹¹Cd. The shift at 80 K was found to be KS (CdPd, 80 K)=?0.8(2)%. The observed variation of the KS in the temperature range from 80 K up to 1400 K is 0.5%. For calibration purposes an accurate remeasurement of the magnetic moment of the 5/2⁺ state in¹¹¹Cd was necessary and yieldedμ(¹¹¹Cd, 5/2⁺, 247 keV)=?0.7697(20) n.m.     

Analysis of the Knight shift for liquid alkali alloys

The Knight shift for binary alkali systems in the liquid phase is analyzed in terms of a simple augmented plane wave approximation (A.P.W.). A proper normalization of the electron wave functions combined with the concentration dependence of the Pauli susceptibility gives a reasonable prediction of the Knight shift of both components as a function of concentration.     

Muon Knight shift at a structural defect in zinc crystals

The interaction of a light hydrogen isotope with a structural defect is traced for the first time by means of the temperature dependence of the muon Knight shiftK in the hcp metal Zn. A surprising result is the huge and negativeK (–520 ppm) at the defect site, probably a multivacancy cluster.     

The109Ag Knight shift in the palladium-silver alloy system

The¹⁰⁹Ag Knight shiftK in the PdAg system has been observed at 298 K. The temperature dependence of the shift is presented in conjunction with the data of Narath at 4 K. The shift is found to be temperature dependent for silver concentrations less than 60 at. %. An analysis ofK in terms of thes andd electron contributions shows that thes electron density of states at the Fermi energy is in agreement with a commons band uniformly filled at the Pd and Ag sites and thatK _d is linearly related to the susceptibility of the PdAg system with both the temperature and the alloy concentration as implicit parameters.     

Spin-orbit effects on Knight shift - a new contribution

We derive an expression for the Knight shift (K) including spin-orbit and many-body effects using fite temperature Green function method. We obtain a new contribution to K which is non-zero only when spin-orbit interaction is taken into account. For p-type PbTe, we find that this contribution is of the same order of magnitude as other contributions which have been considered in the past. The effect of exchange and correlation on this new contribution is discussed briefly.     

Anisotropic μ+ shift in bismuthshift in bismuth

μSR studies in the semi metal Bi have revealed pronounced anisotropies in the μ⁺ Knightshift which vary strongly with temperature. Above 10 K the anisotropy is well described by a P₂(cosθ) distribution with a change of sign around 60 K. Below 10 K we find a very unusual angular dependence in that the anisotropy is described only by terms of fourth order in the direction cosines. Such a dependence is allowed by symmetry arguments, considering that the pointgroup of the crystalline μ⁺ site is D_3d, but requires that the electrons, responsible for the μ⁺ Knight shift, are subject to strong spin orbit coupling or involve effective, field induced moments of orbital origin. The various types of anisotropies seem to be associated with the different site occupations of the μ⁺. The total Knightshift is generally regative which is to be contrasted with the huge positive Knightshift found in the other semimetal Sb /1/.