Magnetic Hyperfine Splitting Research Articles

Mössbauer spectroscopy of Greek ‘Etruscan’ pottery

WE present here an analysis of the iron compounds in both the core and surface ‘gloss’ of a sherd of Greek ‘Etruscan’ black glazed pottery, using both scattering and absorption techniques. The Mossbauer effect1 is used to measure the magnetic hyperfine splitting, determined by the overall magnetic properties and the isomer shift and quadrupole splitting, which are related to the oxidation state and site symmetry at the Mossbauer site. Mossbauer measurements are particularly effective for structures containing iron, even in finely divided form, and are non destructive.

Mössbauer spectra of 237Np in ion exchange resins and in a solvent extractant

Abstract A Mossbauer effect has been observed for Np(IV) ions sorbed on a cation exchange resin from HNO 3 and HCl solutions and for [NpCl 6 ] −2 and [Np(NO 3 ) 6 ] −2 complexes sorbed on an anion exchange resin. Mossbauer spectra have also been recorded for [NpCl 6 ] −2 and [Np(NO 3 ) 6 ] −2 complexes extracted into a tri- n -octylamine-benzene solution. The isomer shifts and quadrupole splitting for the sorbed and extracted species have been found to agree, but the quadrupole splittings were found to differ from those observed for the parent compound in the crystalline state. The Mossbauer spectra for all non-crystalline systems at 4·2°K were found to be dominated by magnetic hyperfine splitting.

LOW TEMPERATURE PHASES OF MICROCRYSTALLINE FeCl3

Mossbauer spectra of FeC13, vapour deposited at low temperatures, show two quadrupole doublets above 6.5 K and magnetic hyperfine splittings below 6.5 K. Upon heating to 300 K the samples can be transformed irreversibly to the normal crystalline phase. Below their magnetic transition temperatures the spectra of both vapour quenched phases and of the normal crystalline phase exhibit relaxation effects which are interpreted as superparamagnetic fluctuations. In contrast to the amorphous ferrous halides, the magnetization curves of the vapour quenched phases of FeC13 show the same functional dependence as the crystalline phase. It is suggested that the low temperature deposition of FeC13 leads to microcrystalline rather than to amorphous structures.

Nuclear excitation and isomer shifts in muonic atoms: (I). Experiment and evaluation

Energies and intensities of 53 nuclear γ-lines in muonic atoms of Sm, Gd, Eu, Tm, Yb, Ta, W, Re, Os, Ir, Pt, Hg, Tl, and Bi have been measured with Ge(Li) detectors. By comparison with γ-lines from radioactive sources the isomer shifts for transitions from nuclear rotational levels, quadrupole and octupole vibrational levels, and single-particle levels have been deduced. The effect limiting the accuracy of the extracted isomer shifts is the correction for the magnetic hyperfine splitting of the nuclear levels.

Mössbauer effect and electron spin resonance of the (iron)4-sulfur clusters of ferredoxin from Clostridium pasteurianum.

Ferredoxin from Clostridiurn pasteurianum which is characterized by two clusters containing four sulfur‐linked iron atoms each, was studied by MöBbaner and elect)ron spin resonance spectroscopy.The iron of oxidized ferredoxin is high‐spin Fe(III) (S=5/2) coupled antiparallel magnetically as conaludcd from the magnitude of the quadrupole splitting and its slight temperature dependence. Thus the net spin of the cluster is 8=0. This explains why no magnetic hyperfine splitting was observed in the Mößbauer absorption spectrum of oxidized ferredoxin at 4.2 K. The observation of at least two quadrupole doublets with a ratio of intensities deviating from unity points to a slight inequivalence of the ligand field symmetry of the individual iron atoms.Reduction of oxidized ferredoxin leads to an uptake of one electron per cluster. The net electron spin of each cluster of reduced ferredoxin is thus S=1/2. Spin‐spin coupling of both the clusters prevents the appearance of a magnetic hyperfine splitting at low temperature. In an external magnetic field of 20 kG the coupling is removed and a hyperfine structure is observed.Under the conditions of X‐band electron spin resonance spectroscopy, i.e. in a magnetic field of 3.5 kG, the spin‐spin coupling is not totally removed. Thedore, an anisotropic 7‐line spectrum originating from a system with S = 1, is observed. Under chemical conditions producing partly reduced ferrcdoxin a 2‐line spectrum from the uncoupled S=1/2 systems is also found. It indicates axial symmetry of the innermolecular electric field. Möβhauer spectroscopy enabled the detection of various amounts of non‐cluster iron in samples of oxidized and reduced ferredoxin.

Theg-factor of the 2+ state of180W and quadrupole moment ratios observed for180W and180Hf by the M�ssbauer technique

By Mossbauer absorption experiments the magnetic hyperfine splitting has been observed for the 2+ states of180W and182W in a tungsten iron alloy (3.6 at%W). Since theg-factor of the 2+ state of182W is known the measured splitting of the182W line could be used for the calibration of the magnetic hyperfine field and the measurement with180W gave then for the unknowng2+-factor of180W: $$g_{2 + } (^{180} W) = 0.260 \pm 0.017.$$ By use of a WO3 absorber the electric quadrupole splittings in the same states were measured. The ratio of the quadrupole moments was derived $$\frac{{Q_{2 + } (^{180} W)}}{{Q_{2 + } (^{182} W)}} = 0.983 \pm 0.022.$$ This ratio is somewhat smaller, but more accurate than the weighted means of previous results and in disagreement with the theoretical prediction.

Mossbauer investigation of the metal-nonmetal transition in hexagonal NiS doped with 2-at%57Fe

The Mossbauer spectra of two compositions of hexagonal Ni1-xS doped with 2%57Fe are obtained at various temperatures from 4.2 to 300 K at Tc=244 K in the first and 221 K in the second, a first-order phase transition occurs between an antiferromagnetic nonmetal and a paramagnetic metal; the magnetic susceptibilities, thermoelectric powers and conductivities change sharply in magnitude with a transition width of 4-5 K. The magnetic hyperfine splittings are fitted by a least squares procedure to a Brillouin function with J=2. The values of the spin disordering temperature TB at which the function cuts the zero-magnetization axis are discussed.

Recalculation of hfs Constants of Muonic Rotational Nuclei

Magnetic hyperfine splittings of rotational levels in muonic deformed nuclei are calculated microscopically within the self-consistent cranking model, taking into account the finite extension of the nucleus. A previous oversight in the theory of the magnetic interaction between the muon and the nucleus is corrected. The splittings are found to be about 25% larger than the earlier estimates. These new values seem to remove the discrepancy between muonic and M\"ossbauer isomer shifts in the rare-earth region.

Mossbauer spectra of trispyrrolidylcarbodithioates of Cr(III), Co(III), Ga(III), and In(III) doped with Fe(III). Evidence of cross relaxation between Fe(III)–Cr(III)

Mossabauer spectra have been measured at 298, 78, and 4.2°K on chromium (III), cobalt(III), gallium(III), and indium(III) trispyrrolidylcarbodithioates containing 1–35 at.% iron(III). At 4.2°K the usual six line pattern due to magnetic hyperfine splitting is observed for the iron(III) doped diamagnetic matrices. However, for the paramagnetic chromium (III) matrix, a five line spectrum is found at iron concentrations of 1–18 at.%, indicating a spin-spin relaxation between iron(III) and chromium(III) ions.

On the magnetic hyperfine splitting in the configuration 4f 7 6s6p of Eul

Experimental results on the hyperfine structure of the z 8P 5 2 - and z 8P 7 2 -levels are presented and discussed by use of intermediately coupled eigenfunctions. Configuration mixing with 4f 7( 8S) 5d6p and 4f 6( 7F) 5d6s 2 is taken into account.

Spin Fluctuations of Fe3+ Ions in Cobalt–Zinc Ferrites Using the Mössbauer Effect

AbstractResonance absorption spectra of Fe57 in CoxZn1−xFe2O4 (for x = 0.3, 0.5, and 0.75), in the temperature range from 80 to 700 °K, are discussed. The modulated lineshapes of the magnetic hyperfine spectra show features which are characteristic of relaxation effects. The theoretical line shapes, computed using the stochastic model, show good agreement with the experimental data at all temperatures for all the three compositions. For each composition, the relaxation time decreases very slowly with increase in the temperature, up to the magnetic transition temperature. Near the Néel temperature, the relaxation time starts decreasing rapidly, leading to the total collapse of the magnetic hyperfine splitting. The introduction of the Zn2+ ions in the ferrite increases the relaxation times at low temperatures (T < TN). The change is, however, negligible for the increase in the Zn2+ concentration from x = 0.5 to 0.3. This behaviour can be attributed to the role of Zn2+ ions in increasing the magnetic disorder in the ferrite. The increase in the concentration of Zn2+ ions causes the damping of the collective modes existing in an ordered ferrimagnetic system.

Raman active lattice spectrum of single crystal 2,4,6-triphenyltriazine

Crystals of hydrated europium bromate were grown and magnetic susceptibilities measured from room down to liquid oxygen temperatures. The effective magnetic moment peff is found todecrease with decreasing temperature indicating a Van Vleck high temperature contribution. The magnetic anisotropy Δχ=χ‖−χ⊥ is negative and appreciable. The magnetic susceptibilities χ‖; and χ⊥ parallel and perpendicular to c-axis, respectively, rise slowly with decreasing temperature, and around 115 K χ⊥ becomes nearly constant while χ‖ decrease slightly; this is quite in contrast to the behavior of other rare earth bromates. A crystal field conforming to D3h symmetry provided a satisfactory explanation to the observed magnetic behavior. The crystal field parameters used are B20=175, B40=−304, B60=−864 and B66=910 all in cm−1. The Schottky heat capacity Cs does not display any anomaly and vanishes below 50 K. Nuclear quadrupole and magnetic hyperfine splitting due to the crystal field has been worked out. The hyperfine heat capacity for both isotopes shows Schottky anomaly below 2 mK.

A pseudopotential based theory of the driving forces for electromigration in metals

Crystals of hydrated europium bromate were grown and magnetic susceptibilities measured from room down to liquid oxygen temperatures. The effective magnetic moment peff is found todecrease with decreasing temperature indicating a Van Vleck high temperature contribution. The magnetic anisotropy Δχ=χ‖−χ⊥ is negative and appreciable. The magnetic susceptibilities χ‖; and χ⊥ parallel and perpendicular to c-axis, respectively, rise slowly with decreasing temperature, and around 115 K χ⊥ becomes nearly constant while χ‖ decrease slightly; this is quite in contrast to the behavior of other rare earth bromates. A crystal field conforming to D3h symmetry provided a satisfactory explanation to the observed magnetic behavior. The crystal field parameters used are B20=175, B40=−304, B60=−864 and B66=910 all in cm−1. The Schottky heat capacity Cs does not display any anomaly and vanishes below 50 K. Nuclear quadrupole and magnetic hyperfine splitting due to the crystal field has been worked out. The hyperfine heat capacity for both isotopes shows Schottky anomaly below 2 mK.

Nuclear Magnetic Resonance on Oriented Platinum-195min Iron

The magnetic hyperfine splitting of $^{195m}\mathrm{Pt}(\mathrm{Fe})$ was determined by the technique of nuclear magnetic resonance on oriented nuclei as $\frac{\ensuremath{\mu}H}{\mathrm{hI}}=89.5\ifmmode\pm\else\textpm\fi{}0.5$ MHz. With additional $\ensuremath{\gamma}$-ray anisotropy data for the 129- and 99-keV $\ensuremath{\gamma}$ rays, we derived the spin, $I=\frac{13}{2}$, and the magnetic moment of the isomeric state, $\ensuremath{\mu}(\frac{13}{2})=\ifmmode\pm\else\textpm\fi{}(0.597\ifmmode\pm\else\textpm\fi{}0.015){\ensuremath{\mu}}_{N}$, as well as the $\frac{E2}{M1}$ mixing ratio of the 99-keV $\ensuremath{\gamma}$ transition, $\ensuremath{\delta}=\ensuremath{-}0.16\ifmmode\pm\else\textpm\fi{}0.02$.

The g-factor of the 130 keV state in 195Pt measured by the Mössbauer effect

Using the Mössbauer effect of the 130 keV transition in 195Pt the g-factor of the first 5 2 − level in 195Pt was derived from magnetic hyperfine splitting in an Pt-Fe alloy: g ( 5 2 −) = 0.35±0.042 . The known g-factors of the if 1 2 - ground state and the 99 keV 3 2 − it possible to determine the magnetic field at the site of the Pt nucleus with high accuracy. The experimental line-widths of the resonance curves are in excellent agreement with lifetime measurements. Comparison of the isomer shift measurements of the 99 keV and the 130 keV transitions give Δ〈r 2〉 130 Δ〈r 2〉 99 = 1.61±0.20 . The experimental results are compared with theoretical calculations.

Metamagnetism in Neptunium(V) Oxalate

Magnetic properties of neptunium(V) oxalate, (NpO2)2C2O4·4H2O, were studied from 2.4 to 37.5°K with magnetic-susceptibility measurements using a vibrating-sample magnetometer at applied fields of 50–10 000 Oe; Mössbauer spectra of the 59.54−keV γ ray in 237Np were taken from 4.2 to 80°K. A metamagnetic transition was found at 11.6°K. Below 11.6°K the magnetization isotherms had the characteristic S shape of metamagnets. Below 8°K a pronounced hysteresis was observed as the field was reduced from saturation. At 3.15°K the remanent magnetization at 100 Oe was 96% of the saturation magnetization at 10 000 Oe, and 125 times greater than the magnetization in the low-moment state. The Mössbauer spectra exhibited magnetic hyperfine splitting which was independent of temperature, with g0μnHeff = 10 cm/sec; splitting above the transition temperature is attributed to a long paramagnetic relaxation time.

Magnetic Properties of Ferrous Chloride Complexes with Two-Dimensional Structures

The quadrupole and magnetic interactions in compounds of the type ${(R\mathrm{N}{\mathrm{H}}_{3})}_{2}\mathrm{Fe}{\mathrm{Cl}}_{4}$, where $R=\mathrm{C}{\mathrm{H}}_{3},{\mathrm{C}}_{2}{\mathrm{H}}_{5},{\mathrm{C}}_{3}{\mathrm{H}}_{7}$, and ${\mathrm{C}}_{6}$${\mathrm{H}}_{5}$C${\mathrm{H}}_{2}$ have been studied. The M\"ossbauer spectra obtained at room temperature showed a quadrupole doublet with $\ensuremath{\Delta}{E}_{Q}=2.1\ensuremath{-}2.3$ mm/sec for all four compounds and an isomer shift I. S. =1.2-1.25 mm/sec referred to stainless steel. The electronic ground state is $^{5}B_{2g}$. The liquid-nitrogen-temperature results showed a magnetic hyperfine splitting for all compounds except the benzyl compound. The internal magnetic field varies from 220 KOe in propyl to 240 KOe in methyl with axis of magnetization in the plane of the sheet. Magnetic-susceptibility measurements for methyl, propyl, and benzyl compounds showed the transition temperatures to be 96, 90, and 72\ifmmode^\circ\else\textdegree\fi{}K, respectively. They also indicated that significant amounts of short-range order above the transition temperature are absent, and the compounds are antiferromagnetic. Finally, ESR calculations gave a $g$ in the range of 2.01-2.015 and a value of $J=8\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}16}$ erg.

Magnetic hyperfine splitting of the99Ru Mössbauer resonance in SrRuO3

The 99Ru Mossbauer spectrum of SrRuO3 at 4·2 K shows a magnetic hyperfine splitting; the internal field of 352 kG at 4.2 K (315 kG at 77 K) is shown to be compatible with the ferromagnetic moment derived from neutron diffraction data, and confirms the collectiveelectron magnetism model for this compound.

Mössbauer study of iron in atmospheric air

Use of the Mossbauer effect has been made for studying iron in atmospheric air. The experiments were performed by observing the absorption of 14.4 keV gamma rays from 57 Co by samples consisting of filters through which atmospheric air was pumped. Using the “area method”, usually applied in calculations of the recoilless raction ( f -factor) the content of natural iron per cubic meter of atmospheric air was found to be 1.4 ? g /m 3 . The measurements were carried out at room and liquid nitrogen temperatures. The room temperature spectra show two absorption lines due to quadrupole splitting; the low temperature spectrum shows a central unresolved doublet and, besides it, six lines due to magnetic hyperfine splitting. From the shapes of the Mossbauer spectra obtained it was inferred that iron appears in the Fe 2 O 3 compound in the form of ultrafine particles (? 100 A) in the superparamagnetic state. DOI: 10.1111/j.2153-3490.1971.tb00560.x

Isomer Shifts of the First and Second Excited Levels of the Ground-State Rotational Band inYb171

The isomer shifts of the 66.7-keV ${\frac{3}{2}}^{\ensuremath{-}}\ensuremath{\rightarrow}{\frac{1}{2}}^{\ensuremath{-}}$ and the 75.9-keV ${\frac{5}{2}}^{\ensuremath{-}}\ensuremath{\rightarrow}{\frac{1}{2}}^{\ensuremath{-}}$ $\ensuremath{\gamma}$ transitions of the \textonehalf{}[521] ground-state rotational band in $^{171}\mathrm{Yb}$ have been investigated, using the M\"ossbauer effect. From the observed shifts, the ratio of change in mean square charge radii for the two excited states was found to be $\frac{\ensuremath{\Delta}〈{r}^{2}〉(76)}{\ensuremath{\Delta}〈{r}^{2}〉(67)}=+0.42\ifmmode\pm\else\textpm\fi{}0.20.$ The decrease of $\ensuremath{\Delta}〈{r}^{2}〉$ for higher rotational excitation is in disagreement with simple collective theory, and is discussed in terms of nonadiabatic effects.From the observed magnetic hyperfine splitting, we also deduced the ratio of nuclear $g$ factors $\frac{g(76)}{g(0)}=+0.411\ifmmode\pm\else\textpm\fi{}0.002.$ This value is in excellent agreement with an earlier measurement and has been used, together with other recent data on all magnetic parameters of the \textonehalf{}[521] band, in discussing the spin polarizations effects. The mixing ratio ${\ensuremath{\delta}}^{2}$ of the $\frac{M1}{E2}$, 66.7-keV $\ensuremath{\gamma}$ transition in $^{171}\mathrm{Yb}$ was redetermined correcting carefully for finite absorber effects. The new result is ${\ensuremath{\delta}}^{2}=0.36\ifmmode\pm\else\textpm\fi{}0.04.$