Hyperfine field of samarium in europium monoxide

The hyperfine magnetic field at samarium in europium monoxide at 4.2 K was measured using the time-differential perturbed angular correlation technique. The resultH _hf=147.9±9.7 T indicates a 4f contribution of 130±20 T which is 60% less than the free ion value for Sm³⁺. It is suggested that there exists crystal plus exchange field interactions causing admixtures of the first excited state of Sm³⁺ with its ground state.     

Hyperfine interactions in chromium

Conclusion Our experiments suggest that Tantalum in Chromium is non magnetic and does not clamp the S.D.W. The various transitions of chromium have been observed. On the other hand rhodium seems to couple with the S.D.W. but the interaction, if any, between rhodium and the S.D.W. does not strongly modify the shape of the S.D.W. TDPAC experiments are therefore a useful tool to investigate the magnetic properties of impurities dissolved in a chromium matrix. This is extremely interesting because the formation of a localized moment in an itinerant antiferromagnet as well as their interaction with the S.D.W.'s have never been studied. It is also interesting to note that S.D.W.'s could couple magnetic impurities at very large distances and then could give rise to a special type of spin glass.     

Hyperfine structure of light exotic atoms

Recoil corrections to the hyperfine structure of light exotic atoms, including the effect of the anomalous magnetic moment are calculated for light muonic and baryonic atoms. In the case of muonic atoms, the effects of recoil and finite nuclear size are significant in view of the presently attainable experimental precision.     

Hyperfine interactions in cubic perovskites

ABO₃ perovskites display several physical properties determined by the characteristics of A and B cations. These compounds have cubic structure at high temperature. Lower symmetry cells that are distorted cubes are found at low temperature. Defects modify the properties of these compounds. Under standard conditions oxygen vacancies are produced. Cation substitution also alters the characteristics of perovskites. These materials have been studied by Perturbed Angular Correlation (PAC) spectroscopy and other hyperfine techniques. In this way abundant information is available to determine charge distributions close to probes. In the cubic phase perturbations were detected that are produced by the interaction of probes with defects. To show up these effects we analyze the quadrupole interaction at ¹⁸¹Ta in several compounds: ABO₃ with A=Ca, Sr and Ba, BaTi_1−x Hf _x O₃ and PbZr_1−x Ti _x O₃ for 0⩽x⩽1. Three different quadrupole interactions were found and are interpreted in terms of distinct probe-oxygen vacancy configurations. This revised version was published online in August 2006 with corrections to the Cover Date.     

Hyperfine interactions in isolated ions

Conclusion It has been demonstrated that the effect of a tilted multifoil array on an ensemble of nuclei approaches a regular precession in a field of magnitude pH in the direction of the tilt axis. The magnitude of the precession can, under certain circumstances, be considerably larger than in a transient field, the only other method available today for measurements in the picosecond range. The technology of multifoil arrays has not been fully mastered to date, the immediate objective being the construction of arrays which keep their shape and spacings for many hours in a particle beam.     

Hyperfine interactions of muonium in alpha-quartz

We present the properties of muonium which are connected with the presence of the muonium quadrupole moment and discuss the results of experimental studies of the quadrupole interactions of muonium with the alpha-quartz lattice.     

Hyperfine interactions in magnetoelectric hexaferrite system

Nuclear magnetic resonance (NMR) in Y-hexaferrite system (Ba_1?xSr_x)₂Zn₂Fe₁₂O₂₂ was measured on both monocrystalline and polycrystalline samples at liquid helium temperature. Corresponding ab-initio calculation of the hyperfine parameters was also performed. The signal from ⁵⁷Fe was detected in the frequency interval 65–76 MHz, while NMR spectrum of ⁶⁷Zn nuclei occurs between 15 and 30 MHz. Due to the disorder in two tetrahedral sublattices occupied partly by Zn and partly by Fe, the NMR lines are broad and the spectra are poorly resolved. Comparison between the experimentally observed ⁶⁷Zn spectra and the spectra modelled using the calculated hyperfine parameters was made. It indicates that the spectra of ⁶⁷Zn can be used to determine the distribution of Zn and Fe between the two tetrahedral sublattices.     

Hyperfine interactions in negative parity baryons

The hyperfine interaction between quarks suggested in chromodynamics can, without free parameters, explain the size and pattern of the splittings and the mixing angles observed experimentally in nonstrange, negative parity baryons.     

Hyperfine interactions in amorphous Tm-Cu Alloys

Hyperfine interactions in sputtered amorphous Tm_xCu_1?x, with x=0.70, 0.50, and 0.33, have been measured over a temperature range from 1.7 K to room temperature using the Mössbauer effect in¹⁶⁹Tm. At low temperatures each spectrum shows a well resolved six-line hyperfine pattern indicative of magnetic order and a superimposed quadrupole doublet. The relative spectral weight of the magnetic component increases with increasing Tm concentration and decreases with increasing temperature. The magnetic component persists at unexpectedly high, temperatures with no decrease in overall splitting and no evidence of electronic relaxation. For all three concentrations, the magnetic splitting is the same as that of Tm metal at low temperatures, nearly the free-ion limit. The electric quadrupole shift of the magnetic component is the same for the three samples, but is significantly less than that of Tm metal (hexagonal) and much larger than that of crystalline TmCu (cubic). The non-magnetic doublets have quadrupole splittings that are very nearly the same for the three concentrations and show considerable asymmetry, a typical effect of electronic relaxation, which persists at temperatures above where the magnetic component disappears.     

Hyperfine interactions in hydrogenated vanadium-iron alloys

The changes in the magnetic properties of disordered bcc V-Fe alloys induced by hydrogenation have been studied by Mössbauer spectroscopy. A shift in the critical composition for the onset of magnetic ordering to lower iron concentration was found in these alloys as a result of hydrogenation.     

Intercalation of graphene on iridium with samarium atoms

Intercalation of graphene on Ir (111) with Sm atoms is studied by methods of thermal desorption spectroscopy and thermionic emission. It is shown that adsorption of samarium at T = 300 K on graphene to concentrations of N ≤ 6 × 10¹⁴ atoms cm^–2 followed by heating of the substrate leads to practically complete escape of adsorbate underneath the graphene layer. At N > 6 × 10¹⁴ atoms cm^–2 and increasing temperature, a fraction of adsorbate remains on graphene in the form of two-dimensional “gas” and samarium islands and are desorbed in the range of temperatures of 1000–1200 K. Samarium remaining under the graphene is desorbed from the surface in the temperature range 1200–2150 K. Model conceptions for the samarium–graphene–iridium system in a wide temperature range are developed.     

Hyperfine field at grain boundary atoms in iron nanostructures

Iron nanocrystallites of ball-milled iron powder, partially crystallized melt quenched amorphous alloys and polycrystalline multilayers were studied. The change in the hyperfine field at iron atoms due to grain boundaries does not exceed the experimental linewidth. This revised version was published online in August 2006 with corrections to the Cover Date.