Knight shift of sp-elements in bismuth

A large negative term in the Knight shift has been found for a number of open p-shell elements of the 5th and 6th period in the host Bi which disappears at the p-shell closure.The authors would like to acknowledge the fruitful discussions with R.E. Watson.     

Temperature dependence of the positive-muon knight shift in MnSi

The temperature dependence of the μ⁺ Knight shift in weakly-helimagnetic MnSi has been measured in the temperature range between 28 and 300 K. The observed shift is found to be directly proportional to the host susceptibility in the paramagnetic state with a hyperfine coupling constant of —4.8 kOe/_μB.     

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.     

Temperature dependence of the nuclear quadrupole interaction and the Knight shift in rhenium metal

The temperature dependences of the static nuclear quadrupole interaction and the Knight shift in rhenium metal were investigated for 2K ≦ T ≦150 K by the method of Nuclear Acoustic Resonance (NAR). For the quadrupole interaction ¦e²qQ/h¦ an increase occurs from 255.2(5) MHz at 2 K to 257.2(8) MHz at 150 K in¹⁸⁷Re [269.5(7) to 271.5(10) in¹⁸⁵Re] whereas for the Knight shift a slight decrease from 1.14(4)% at 2K to 1.10(8)% at 150 K [1.16(6) to 1.12(10)] is found.     

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.     

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.     

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.     

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.     

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.     

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.     

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.     

Temperature dependence of the muon Knight shift in graphite measured using a μSR\times 2 method

We describe a simple method by which time differential μSR spectra are collected on two different samples simultaneously. One application is to make accurate measurements of the muon precession frequency in a sample relative to a reference. As an example we report precise measurements of the muon Knight shift on HOPG graphite with H parallel to \hat c as a function of temperature. This revised version was published online in August 2006 with corrections to the Cover Date.     

Anomalous field dependence of muon Knight shift and line width in the singlet ground state compound PrCu2

We report on ZF and TF‐studies of PrCu₂ above the induced Jahn–Teller transition at 7.3 K. Generally a two‐component signal is found, one showing inhomogeneous the other one homogeneous, temperature dependent line broadening. In ZF the former component is well represented by a Gaussian Kubo–Toyabe function with \varDelta \simeq 6.5\,μs^-1 at 7.5 K, corresponding to a field width of 76 G. This is about 30 times larger than what is calculated to arise from the ¹⁴¹Pr‐nuclear dipole moments alone, pointing to strong hyperfine enhanced features. TF‐field scans at 12 K revealed that the enhancement is suppressed in external fields exceeding 1 kG. In parallel the Knight shift drops from very large values well above 10% at 100 G to shifts of the order of 1% above 1 kG. A scaling of the Knight shifts with the corresponding relaxation rates seems to imply that the strange field dependence below 1 kG is associated with the magnetic susceptibility of the muons’s nearest neighbour Pr³⁺‐ions, a result for which we have no explanation yet to offer. This revised version was published online in July 2006 with corrections to the Cover Date.     

Measurement of the field dependence (Knight shift) of the hyperfine field at a positive muon in ferromagnetic nickel

The dependence of the hyperfine field at an interstitial positive muon in ferromagnetic field has been measured at room temperature yielding a Knight Shift constant K = 0.0025 (3). This Knight shift is interpreted in terms of the Pauli spin paramagnetism of s-p band electrons.     

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.