Magnetic Hyperfine Splitting Research Articles

NMR-ON measurements of187WFe,182,183,186ReNi,186ReFe and203PbFe

The magnetic hyperfine splitting frequencies of187WFe,182Re(jπ=2+)Ni,183ReNi,186ReNi,186ReFe and203PbFe in a zero external magnetic field have been determined by the NMR-ON method at about 7 mK as 225.56(6), 130.9(1), 98.17(4), 136.6(4), 1007.0(3) and 58.43(3) MHz, respectively. With the knowng-factors ofg(186Re, 1−)=1.739(3) andg(203Pb, 5/2−)=0.27456(20), the following hyperfine fields were deduced:BHF(186ReNi)=−103.05(35) kG;BHF(186ReFe)=−759.7(13) kG;BHF(203PbFe)=+279.18(25) kG. Taking hyperfine anomalies into account, theg-factor of183Re was deduced as |g(183Re, 5/2+)|=1.267(6). With the assumption of Knight shift factorK=0, theg-factors of182Re and187W and the hyperfine field of187WFe were determined as |g(182Re, 2+)|=1.63(5), |g(187W, 3/2−)|=0.414(10) andBHF(187WFe) =−714(18) kG. The large hyperfine anomaly was deduced to be183W Δ187W =−0.124(22).

Magnetism of Eu(BrO 3) 3·9H 2O and the crystal field

Crystals of hydrated europium bromate were grown and magnetic susceptibilities measured from room down to liquid oxygen temperatures. The effective magnetic moment p eff is found todecrease with decreasing temperature indicating a Van Vleck high temperature contribution. The magnetic anisotropy Δ χ= 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 D 3h symmetry provided a satisfactory explanation to the observed magnetic behavior. The crystal field parameters used are B 20=175, B 40=−304, B 60=−864 and B 66=910 all in cm −1. The Schottky heat capacity C s 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 11/2? 129mXe and131mXe in Fe

The magnetic hyperfine splitting frequenciesν M=¦gμ NBHF/h.¦ of the 11/2− isomeric states129m Xe (T1/2=8.9d) and131mXe (T1/2=11.8d) in Fe were measured with nuclear magnetic resonance on oriented nuclei at temperatures of 10–15 mK as 188.0(1) MHz and 209.8(1) MHz, respectively, the samples being prepared with the technique of recoil implantation after (α, x n) reactions. The magnetic moments of129m Xe and131m Xe are deduced to be (−)0.8914(6)μ N and (−)0.9943(6)μ N, respectively. The missing γ-anisotropies for allγ-transitions following the decay of 36.4d 127Xe indicateI=1/2 for the ground state spin of127Xe.

A reformulation of the theory of field isotope shift in atoms

The theory of the field isotope shift (FS) in atomic spectra is discussed critically and the results are presented in a form which is more straightforward than the expressions traditionally used to interpret experimental data. First-order perturbation theory is applied within the single-particle framework to the case of an s or p1/2 electron outside closed shells. Parameters to take account of many-body effects are subsequently included. The nuclear and electronic dependences of the FS are separately discussed. In a generalisation of the work of Seltzer (1986), it is shown that the former can be represented as a series of even charge moments: the coefficients of the first three terms for an s electron are given. The difference between the series for an s and a p1/2 electron is shown to be generally insignificant. The electronic dependence enters through the (relativistic) probability density N of the electron at the origin; for the case of an s electron. They relate N to the magnetic hyperfine splitting factor alpha s. A table which allows N to be found from a measurement of alpha s is given. Second-order field shifts are of the order of 10-3-10-4 of the first-order shifts for a two-neutron change.

Magnetic hyperfine splitting in superparamagnetic particles in external magnetic fields

The magnetic hyperfine splitting in Mössbauer spectra of superparamagnetic particles, induced by an external magnetic field, has been calculated. Numerical results have been obtained both for isolated particles with a finite value of the magnetic anisotropy energy constant and for strongly interacting particles. Moreover, analytical approximations are derived. The theoretical results are compared with results of experimental studies of supported α-Fe particles and magnetic particles in ferrofluids.

A spin-orbit 2 1Π g ∼ 2 3Π 2 g perturbation in Na 2: Hyperfine splittings, perturbation matrix elements, and electronic structure implications

A perturbation between the Na 2 2 3Π 2 g v = v ∗ − 11 ( v ∗ = 68 ± 2 ) and 2 1Π g v = 27, J = 13 and 14 levels is observed by Perturbation Facilitated Optical-Optical Double Resonance Spectroscopy. The local ( J = 13) and electronic spin-orbit perturbation matrix elements, respectively, are 0.096(13) and ∼3.5 cm −1 (1σ uncertainty). The relatively large size of the interaction matrix element implies that the 2 3Π g and 2 1Π g states both have appreciable π g ∗3p LCAO-MO character at short internuclear distance (the potential curves cross near R = 3.4 A ̊ ). The 2 3Π 2 g v = v ∗ − 11 , J = 13 and 14 levels are observable by virtue of their admixed 2 1Π g v = 27 character (20 and ∼5%, respectively), but the resolved magnetic hyperfine splitting C J13 e= -4.73(21)MHz, C J13 f= -5.10(63)MHz C J14 f= -4032(29)MHz, C J14 e= -4.13(30)MHz reflects the mixed-Ω 2 3Π g character of these levels. The hfs in the 2 3Π 2 g state is very similar to that in b 3Π 2 u (1 3Π u ) because the hfs originates primarily from the σ g 3 s orbital which is nominally singly occupied for both 3Π states.

High-power pulsed dye laser with Fourier-limited bandwidth

A high-peak-power, narrow-linewidth light source with a homogeneous beam profile has been constructed by modifications to a commercially available pulsed-dye-laser system. Output pulses of up to 10 mJ were generated with linewidths of about 50 MHz for 12-nsec pulses. The pulse-to-pulse frequency stability was better than the linewidth, and the center frequency could be scanned over a frequency range of 142.5 GHz at a wavelength of 600 nm. The performance of the system was demonstrated by observing the 6s2 1S0–6s7s1S0 transition in atomic mercury at 2λ = 312.8 nm and the 6s2S1/2–8s2S1/2 transition in atomic gold at 2λ = 308.9 nm using up to 1 mJ of frequency-doubled output for two-photon nonlinear absorption spectroscopy. The lifetimes of both excited states, the magnetic hyperfine splitting of the 8s2S1/2 state in gold, and the isotope shift of the 6s7s1S0 state of mercury were determined.

Magnetic properties of NpM4Al8−x (M=Cr, Fe, Cu) intermetallics: Mössbauer effect and neutron diffraction studies

Mossbauer effect and neutron diffraction studies on the tetragonal NpM4Al8−x (M=Cr, Fe, Cu) of the 14/mmm space group are reported. In NpFe4Al8−x, both the Np and Fe sites order magnetically at close temperatures: the Np order ferromagnetically at 115(15) K (μ(Np)) ∼ 0.6 μB and the Fe moments order antiferromagnetically at 130(10) K (μ(Fe) = 1.05(15) μB) with a ++−− sequence. In NpCr4Al8−x, the Np order magnetically around 50K. From the susceptibility data we conclude possible antiferromagnetic order of both Np and Cr sites. NpCu4Al8−x does not order magnetically down to at least 2 K. The magnetic hyperfine splitting observed below 45 K is explained by slow paramagnetic relaxation. The Np isomer shifts and also its magnetic behavior point to a trivalent ion (5I4 Hund's rule ground state). The observed relaxation and magnetic phenomena are discussed in terms of crystalline electric field effects. In contrast to the isostructural rare-earth RM4Al8 compounds with practically independent order of R and M magnetic sublattices, we show that Np and M sublattices in NpM4Al8 are strongly coupled. This is caused by hybridization of both Np and M atoms with Al.

Oxygen Order, Stoichiometry and Magnetic Behavior of YBa2(Cu1−xFex)3O7+δ

ABSTRACTMössbauer effect and neutron diffraction measurements have been made as a function of composition for YBa2(Cu1−xFex)3O7+δ. A chemically driven disordering of the sublattices is observed with increasing Fe concentration which results in a transition from the orthorhombic to a tetragonal phase. However, as the occupancy of the oxygen site 0(1) in the chain is depleted and the site of the ordered vacancy 0(5) between the chains becomes occupied, the total oxygen content is not reduced but remains near seven in contrast to behavior observed in the quenched tetragonal phases. Mössbauer spectra for x =0.05 at temperatures below 15K show magnetic hyperfine splitting which is characteristic of a spin glass; i.e., a distribution of magnetic fields. It is inferred from Mössbauer results that Fe preferentially occupies the Cu(1) site.

Magnetic properties of the R1+ eFe 4B 4 compounds ( R = rare earth) from magnetization and Mössbauer measurements

The magnetic properties of rare earth-iron-boron alloys with composition R 1+ e Fe 4B 4 have been determined using Mössbauer and magnetization measurements. Magnetic ordering occurs at temperatures between 4.2 and 25 K for the compounds with R = Pr, Nd, Sm, Gd, Tb, Dy, Ho. The Curie temperature scales very well with the de Gennes factor for the heavy rare earth members of the series, while significant deviations are observed for the light rare earths indicating the presence of strong CEF effects. The absence of magnetic hyperfine splitting even at 4.2 K indicates that the Fe ion has a zero magnetic moment. This is confirmed by Mössbauer spectra in an applied magnetic field.

An intermodulated fluorescence study of the A2Σ−-X2Πi band system of copper monoxide

Abstract Several lines in the A 2 Σ − ( v = 0)- X 2 Π i ( v = 0) visible band system of gas phase copper monoxide have been measured at sub-Doppler resolution using the technique of intermodulated fluorescence. The copper nuclear magnetic hyperfine splitting is clearly resolved. The observations were fitted to an effective Hamiltonian model and values of the magnetic hyperfine parameters of b F = −0.0302 cm −1 for the A state and d = 0.0024 cm −1 for the X state were determined. An interpretation of these values in terms of the proposed electronic configurations of these states is presented.

Magnetic moment of the 5/2?1/2[541] ground state of 14h 185Ir

The magnetic and electric hyperfine splitting frequencies ¦gμ N B HF/h¦ ande 2 qQ/h of the 5/2−1/2[541] ground state of 14h 185Ir in Ni were measured with nuclear magnetic resonance on oriented nuclei to be 360.8(7) MHz and +6.7(2.0) MHz, respectively. The ground state magnetic dipole moment and electric quadrupole moment of185Ir are deduced to be ¦μ¦=2.601 (14)μ N andQ=−1.9(5)b, taking values for the hyperfine field and electric field gradient of BHF=−454.9 (2.3) kG and eq=−0.151(4) × 1017 V/cm2, respectively. The negative quadrupole moment is in agreement with nuclear-orientation data and proves again theI π K=5/2− 1/2 ground state configuration.

Topochemical lithium insertion into Fe 2(MoO 4) 3: Structure and magnetism of Li 2Fe 2(MoO 4) 3

Powder X-ray diffraction, variable temperature magnetic susceptibility, and zero-field Mössbauer spectroscopy measurements were used to characterize the new phase Li 2Fe 2(MoO 4) 3. This material is obtained simply by the mixing of solutions of lithium iodide in acetonitrile with solid Fe 2(MoO 4) 3 at ambient temperature. The reaction is entirely reversible using bromine as an oxidant. Li 2Fe 2(MoO 4) 3 possesses the high-temperature orthorhombic ferric molybdate structure and Guinier photographs were completely indexed in space group Pnca with cell constants a = 9.3483(5), b = 12.8974(9), and c = 9.4941(6) Å versus the monoclinic ( P2 1 a ) Fe 2(MoO 4) 3 precursor phase. Chemical analytical data, room-temperature magnetic susceptibility and Mössbauer spectroscopy indicate essentially complete stoichiometric reduction of the latter compound. Magnetic hyperfine splitting of the zero field Mössbauer spectrum below 12.5 K indicates a three-dimensional magnetically ordered state which susceptibility results show to be weakly ferromagnetic owing to probable canting of antiferromagnetically coupled lattices. Above ∼40 K, the material obeys a Curie-Weiss law whose parameters are C = 3.51 emu/mole, μ eff = 5.30 β and ϑ = −19 K.

Detection of nuclear magnetic resonance on oriented 193mPtFe via the anisotropy of characteristic x rays.

Nuclear magnetic resonance on oriented nuclei has been detected for the first time via the resonant change of the radiation pattern of characteristic $L$ x rays. The magnetic hyperfine splitting $|g{\ensuremath{\mu}}_{N}\frac{{B}_{\mathrm{hf}}}{h}|$ of ${\frac{13}{2}}^{+}^{193m}\mathrm{Pt}$ in Fe was determined to be 111.3 (3) MHz. With ${B}_{\mathrm{hf}}=\ensuremath{-}1261(25)\mathrm{kG}$, the $g$ factor is deduced to be (-)0.1158(23). This value differs strongly from the known $g$ factors of ${({\ensuremath{\nu}i}_{\frac{13}{{2}^{+}}})}^{\ensuremath{-}n}$ states in Hg, Pb, and Po, suggesting a significant change in the nuclear-deformation parameters of $^{193m}\mathrm{Pt}$.

Influence of hydrogen absorption on the electronic structure of V-Fe alloys

The results of the Mossbauer spectroscopy investigation of the hydrogenated V-Fe alloys show a distinct changes in both the isomer shift and the line-width of the Mossbauer spectra when the mean electron concentration of the alloy exceeds 5.6 el./at. No magnetic hyperfine splitting is observed in the spectra. It seems that the tetragonal deformation of the crystalline structure of the alloys, related to the hydrogen absorption, is responsible for the generation of the localized magnetic moments on the Fe atoms in the alloy with ne> 5.6 el./at.

A review of Mössbauer spectroscopic studies of ancient pottery

Mossbauer spectroscopy has proven itself to be invaluable to archaeologists by providing a means to classify pottery and to provide information on particular providences for various ancient pottery finds. The original firing atmosphere can often by deduced from the ratio of Fe2+ to Fe3+. The change in the quadrupole splitting and the magnetic hyperfine splittings allow for the determination of the original firing temperatures. Ancient pottery samples from many cultures have been studied and a number of general conclusions are possible.

Low temperature Mössbauer spectra and magnetic ordering of lithiated ferric molybdate: Li2Fe2(MoO4)3

Powder x-ray diffraction, variable temperature magnetic susceptibility, and zero field Mossbauer spectroscopy measurements were used to characterize the new phase Li2Fe2 (MoO4)3. This material is obtained topochemically simply by the mixing of solutions of lithium iodide in acetonitrile with solid Fe2(MoO4)3 at ambient temperature. Li2Fe2(MoO4)3 possesses the high temperature orthorhombic ferric molybdate $$\begin{gathered} Fe_2 (MoO_4 )_3 + 2LiI\xrightarrow{{CH_3 CN}}Li_2 Fe_2 (MoO_4 )_3 + I_2 \hfill \\ (solid)(solution)(solid)(solution) \hfill \\ \end{gathered}$$ structure. Guinier photographs were completely indexed in space group Pnca. Magnetic hyperfine splitting of the zero field Mossbauer spectrum below 12.5 K indicates a three-dimensional magnetically ordered state which susceptibility results show to be weakly ferromagnetic owing to probable canting of antiferromagnetically coupled sublattices.

G-Factors of the ground states of 95Nb and 96Nb

Nuclear magnetic resonance measurements have been performed for 95 Nb and 96 Nb oriented at 7 mK in an Fe host. The magnetic hyperfine splitting frequencies, v = ∥ gμ N B h.f/ h∥, of the 95Nb and 96Nb ground states were determined to be 275.16(8) and 167.20(1) MHz. With a hyperfine field of B h.f. = — 264.54(19) kG the nuclear g-factors were deduced to be ∥g( 95 Nb, 9 2 +)∥= 1.3645(13) and ∥g( 95 Nb, 6 +)∥ = 0.8292(7) .

Mössbauer Spectroscopy and X-Ray Diffraction Studies of Fe-Ni Order-Disorder Processes in a 35% Ni Meteorite (Santa Catharina)

The composition and structure of iron-nickel alloys in the Santa Catharina iron meteorite were investigated by metallographic techniques, electron microprobe analysis, Mössbauer spectroscopy and X-ray diffraction.The occurrence of an ordered Fe-Ni phase with non-cubic symmetry is demonstrated. This phase is present in large proportions in the Santa Catharina meteorite, and has been identified by its asymmetric Mössbauer spectrum, arising from the presence of a quadrupolar splitting superposed on the magnetic hyperfine splitting. The other major Fe-Ni phase in Santa Catharina gives rise to a single line Mössbauer spectrum with no hyperfine components.X-ray diffraction confirms the presence of the Fe-Ni Llo superstructure in this meteorite. Lattice parameter variations with temperature were found to be identical for the meteorite and for electron irradiated Fe-Ni alloys of the sample composition.Detailed Mössbauer spectroscopy studies from room temperature to liquid helium, and in the presence of external magnetic field show the presence of a smaller amount of another ferromagnetic Fe-Ni phase, probably with disordered structure.The destruction of the superstructure in the Santa Catharina meteorite was investigated after heating the samples. Partial ordering seems to coexist with the disordered phase at intermediate annealing temperatures. At higher temperatures the samples are homogenous and similar to laboratory produced Fe-Ni alloys with 35% Ni.Order-disorder transformations produced by shock waves and by mechanical treatment are also described.

Oblate ground-state shapes of 11 h 189Pt and 2.8 d 191Pt

Abstract With nuclear orientation on 11 h 3 2 −189 Pt , 2.8 d 3 2 −191 Pt and 4.0 d 13 2 + 195 m Pt in Os and NMR on oriented 189Pt and 191Pt in Fe electric and magnetic hyperfine splitting frequencies were measured. The nuclear moments are deduced to be: 189Pt: |μ| = 0.434(9) μN, Q = −0.65(26) b; 191Pt: |μ| = 0.500(10) μN, Q = −0.64(26) b; 195mPt: Q = +1.42(60)b. The negative spectroscopic ground-state quadrupole moments of 189Pt and 191Pt must be due to oblate ground-state deformations, thus indicating that the prolate-oblate phase transition in Pt is located at A