Magnetic Hyperfine Parameters Research Articles

Mössbauer and magnetization measurements of multicomponent iron garnets

Four Gd-containing iron garnets were investigated using Mössbauer spectroscopy and Vibrating Sample Magnetometry over a wide temperature range, from 4K to ∼600K. The magnetic ordering temperature and hyperfine parameters determined on the basis of Mössbauer spectra for all samples were found to be surprisingly similar, differences were only noted for the average magnetic moments, which turned out to be strongly correlated with the magnetic moments of rare earth elements present in the structure. Further differences between the systems were also highlighted in measurements in the external 9T magnetic field, especially around the compensation temperature. Changes in the nature of the Mössbauer spectra were interpreted based on the crystal field approximation confirming the correctness of the interpretation of the temperature dependence of magnetization for these samples.

Construction and commissioning of the collinear laser spectroscopy system at BRIF

We have constructed a collinear laser spectroscopy (CLS) system installed at the Beijing Radioactive Ion-beam Facility (BRIF), aiming to investigate the nuclear properties of unstable nuclei. The first on-line commissioning experiment of this system was performed using the continuous stable (39K) and unstable (38K) ion beams produced by impinging a 100-MeV proton beam on a CaO target. Hyperfine structure spectra of these two isotopes are reasonably reproduced, and the extracted magnetic dipole hyperfine parameters and isotope shift agree with the literature values. The on-line experiment demonstrates the overall functioning of this CLS system, opening new opportunities for laser spectroscopy measurement of unstable isotopes at BRIF and other radioactive ion beam facilities in China.

Magnetic Characterization of Co and Zn Nano Ferrites: Property Consideration for Oil-Spill Clean Up

Nano-magnetic particles are significantly finding applications in environmental remediation. This work studied the magnetic properties of Co and Zn nano-ferrites, CoFe2O4 and ZnFe2O4 respectively, with considerations for the properties that are desirable for oil spill cleanup. The ferrite nanoparticles were synthesized by the glycol-thermal method at 200 ºC for 6 hours using a stirred pressure reactor. Single phase spinel crystal structures were obtained for both samples as determined by an X-ray diffraction (XRD) machine. The high-resolution transmission electron microscope and surface electron microscope images showed nano structures. The magnetic properties and magnetic hyperfine parameters were determined using a lakeshore vibrating sample magnetometer and 57Fe Mössbauer spectroscopy. The XRD peaks were consistent with that of a single phase spinel structure. No impurity phase was detected. The nano-ferrites have crystallite sizes of about 10 nm and 17 nm for CoFe2O4 and ZnFe2O4. The nano almost-spherical nature of the samples was also confirmed from their morphology studies. The saturation magnetization of CoFe2O4 and ZnFe2O4 were about 50 emu/g and 30 emu/g respectively. They both exhibited superparamagnetic properties with a component of para-magnetism observed in ZnFe2O4 nano-ferrites. CoFe2O4 nano-ferrites exhibited better desired property for oil spill cleanup. The ZnFe2O4 nano-ferrites showed tendencies of slow response to magnetic field, however, it is more environmentally friendly. The magnetic hyperfine parameters and the isomer shift values for CoFe2O4 and ZnFe2O4 showed strong internal magnetic fields and the obtained values are consistent with spinel structure. The oxidation state of Fe was observed to be Fe3+. Due to the low coercivity and high magnetization values, these particles could be considered as potential candidates for oil spill cleanup. These desirable magnetic properties will improve the recyclability of the nanoparticles using low applied magnetic fields.

Magnetic and Mössbauer Effect Study of Ca-Sc Co-doped M-Type Strontium Hexaferrite

The present study investigates the influence of Ca2+-Sc3+ co-dpoing on the magnetic properties of Sr1-x/12Cax/12Fe12-xScxO19 (x = 0.0 to 2.0) hexaferrites. The samples were prepared via a facile autocombustion technique followed by sintering in ambient air. X-ray powder diffraction patterns show the formation of the pure phase of M-type hexaferrite. The lattice parameters a and c increased with the Ca2+-Sc3+ doping. The compounds’ magnetic properties were assessed as a function of temperature (10–300 K) and field (up to 6T). A rapid decline in room temperature coercivity from 5458 to 373 Oe and remanence value from 37 to 13 emu/g and a moderate decline in saturation magnetization from 76.9 to 57 emu/g were observed with increasing doping content from x = 0.0 to 2.0. The phase transition temperature, corresponding to ferrimagnetic to conical, was observed below 100 K, which disappeared at low doping content. The temperature-dependent behavior of magnetization and coercivity is discussed in view of spin non-collinearity due to the change in magnetic anisotropy. The Curie temperature dropped from 769 K at x = 0 to 568 K at the maximum substitution of x=2.0. The room temperature Mossbauer spectral analysis confirmed the preferred occupancy of Sc3+ at the 4f2 site and the influence of Ca2+ on the isomer shift values of the 2b site. The increased quadrupole shift values with the substitution implied distortion in 2b bipyramidal symmetry. The observed changes in magnetic properties and hyperfine parameters are ultimately tied to the preferred occupancy of Sc3+ at the spin-down 4f2 site.

Flux growth, structure refinement and Mössbauer studies of Fe1-xGaxBO3 single crystals.

High-quality Fe1-xGaxBO3 single crystals (0.0 ≤ x ≤ 1.0) in the form of basal plates were synthesized by the flux technique. The exact content of Fe and Ga and homogeneity of their distribution in the crystal structure were determined by energy-dispersive X-ray spectroscopy. The crystal structure was refined using single-crystal X-ray diffraction data. The electronic and magnetic properties were studied using Mössbauer spectroscopy. It is shown that even a small content of diamagnetic gallium leads to a rearrangement of the crystal structure and essentially changes the magnetic hyperfine parameters of the crystals.

High-resolution spectroscopy of the [18.4]2.5 – X2Δ5/2 transition of ruthenium monoboride (RuB)

Laser-induced fluorescence spectra of the (0, 0), (1, 0) and (0, 1) bands of the [18.4]2.5 – X2Δ5/2 transition have been recorded at high-resolution for several isotopologues of ruthenium monoboride (RuB). We report band origins and rotational parameters for 12 of the 14 possible isotopologues (7 for each of Ru11B and Ru10B) as well as hyperfine parameters of 99RuB and 101RuB. An anomalous isotope shift in the (0, 0) and (0, 1) bands indicates a weak perturbation in the [18.4]2.5 v = 0 vibrational level. The observed hyperfine structure is mainly due to the nuclear spin (I = 5/2) of the two Ru isotopes. Hyperfine structure due to the 11B and 10B isotopes was not resolved and resulted in, at most, a slight broadening of the lines. The magnetic hyperfine parameters help to confirm the (11σ)2(5π)4(2δ)3 configuration of the ground electronic state and provide insight into the configuration of the excited states.

Characterization of gas-phase thorium nitride.

Properties of gas-phase thorium nitride, ThN, have been experimentally determined from a combined optical and microwave spectroscopic study. An intense band near 555 nm has been assigned as the [18.0]1.5-X2Σ+ (0,0) transition and recorded at high resolution in the presence of static electric and magnetic fields. The observed optical Stark shifts were analyzed to determine permanent electric dipole moments, μ→el for the [18.0]1.5 and X2Σ+ states of 4.38 ± 0.02D and 5.11 ± 0.09D, respectively. Zeeman shifts were used to determine the magnetic g-factors. The pure rotational spectrum was recorded using a separated field optical pump/probe microwave repopulation scheme and analyzed to determine the bond length and 14N magnetic hyperfine and nuclear electric quadrupole parameters. A molecular orbital correlation diagram and ligand field electronic structure models are used to provide a qualitative interpretation of the electronic state ordering, magneto- and electro-static properties, and hyperfine interactions. Electronic structure calculations for the X2Σ+ state were performed, and results were compared with observations. Observed trends in μ→el for the ThX (X = N, S, O, F, and Cl) series are discussed.

The pure rotational spectrum of YbOH

The pure rotational spectrum of YbOH has been recorded and analyzed to produce fine and magnetic hyperfine parameters for the X∼2Σ+(0,0,0) state. These parameters are compared with those determined from the optical study (Melville and Coxon, 2001) and with the values for YbF (Dickinson et al., 2001). The results support the existence of an unobserved perturbing state near the A∼2Π1/2 state, similar to that previously found in YbF. The precisely determining parameters lays the foundation for laser cooling YbOH, which will aid in the search for new physics beyond the standard model.

First principles study of the ground state properties of Si, Ga, and Ge doped Fe50Al50

The first principles calculation of the structural, electronic and associated properties of the Fe50Al50 alloy (B2 phase) doped by s-p elements (Im = Si, Ga, and Ge) are performed as a function of the atomic concentration on the basis of the Full Potential Linear Augmented Plane Wave (FP-LAPW) method as implemented in the WIEN2k code. The Al substitution by Im (Si and Ge) atoms (principally at a concentration of 6.25 at%) induces a pronounced redistribution of the electronic charge leading to a strong Fe-Im interaction with covalent bonding character. At the same time, decrease the lattice volume (V) while increase the bulk modulus (B). For the alloys containing Ga, the Fe-Ga interaction is also observed but the V and B of the alloy are very near to that of pure Fe-Al alloy. The magnetic moment and hyperfine parameters observed at the lattice sites of studied alloys also show variations, they increase or decrease in relation to that in Fe50Al50 according to the Im that substitutes Al.

Structural, optical and magnetic studies of CuFe2O4, MgFe2O4 and ZnFe2O4 nanoparticles prepared by hydrothermal/solvothermal method

In this paper we report the structural, optical and magnetic studies of three spinel ferrites namely CuFe2O4, MgFe2O4 and ZnFe2O4 prepared in an autoclave under the same physical conditions but with two different liquid medium and different surfactant. We use water as the medium and trisodium citrate as the surfactant for one method (Hydrothermal method) and ethylene glycol as the medium and poly ethylene glycol as the surfactant for the second method (solvothermal method). The phase identification and structural characterization are done using XRD and morphological studies are carried out by TEM. Cubical and porous spherical morphologies are obtained for hydrothermal and solvothermal process respectively without any impurity phase. The optical studies are carried out using FTIR and UV–Vis reflectance spectra. In order to elucidate the nonlinear optical behaviour of the prepared nanomaterial, open aperture z-scan technique is used. From the fitted z-scan curves nonlinear absorption coefficient and the saturation intensity are determined. The magnetic characterization of the samples is performed at room temperature using vibrating sample magnetometer measurements. The M−H curves obtained are fitted using theoretical equation and the different components of magnetization are determined. Nanoparticles with high saturation magnetization are obtained for MgFe2O4 and ZnFe2O4 prepared under solvothermal reaction. The magnetic hyperfine parameters and the cation distribution of the prepared materials are determined using room temperature Mössbauer spectroscopy. The fitted spectra reveal the difference in the magnetic hyperfine parameters owing to the change in size and morphology.

Examining transition metal hydrosulfides: The pure rotational spectrum of ZnSH (X̃2A').

The pure rotational spectrum of the ZnSH (X̃2A') radical has been measured using millimeter-wave direct absorption and Fourier transform microwave (FTMW) methods across the frequency range 18-468 GHz. This work is the first gas-phase detection of ZnSH by any spectroscopic technique. Spectra of the 66ZnSH, 68ZnSH, and 64ZnSD isotopologues were also recorded. In the mm-wave study, ZnSH was synthesized in a DC discharge by the reaction of zinc vapor, generated by a Broida-type oven, with H2S; for FTMW measurements, the radical was made in a supersonic jet expansion by the same reactants but utilizing a discharge-assisted laser ablation source. Between 7 and 9 rotational transitions were recorded for each isotopologue. Asymmetry components with Ka = 0 through 6 were typically measured in the mm-wave region, each split into spin-rotation doublets. In the FTMW spectra, hyperfine interactions were also resolved, arising from the hydrogen or deuterium nuclear spins of I = 1/2 or I = 1, respectively. The data were analyzed using an asymmetric top Hamiltonian, and rotational, spin-rotation, and magnetic hyperfine parameters were determined for ZnSH, as well as the quadrupole coupling constant for ZnSD. The observed spectra clearly indicate that ZnSH has a bent geometry. The rm(1) structure was determined to be rZn-S = 2.213(5) Å, rS-H = 1.351(3) Å, and θZn-S-H = 90.6(1)°, suggesting that the bonding occurs primarily through sulfur p orbitals, analogous to H2S. The hyperfine constants indicate that the unpaired electron in ZnSH primarily resides on the zinc nucleus.

Hyperfine structure in the X8, A[19.1]9 and B[21.68]8 states of HoF and X8 and A[15.6]9 state of HoCl

High resolution spectra of holmium monofluoride, HoF and holmium monochloride, HoCl, prepared in a laser ablation source, have been obtained using laser induced fluorescence. Spectra of the A[19.1]9–X8 0-0 and 1-0 and B[21.68]8–X8 0-0 bands of HoF and the A[15.6]9–X8 0-0 band of HoCl all show resolved hyperfine structure. Analysis of the spectra yielded magnetic hyperfine parameters, h=0.2240(5), 0.2210(6), 0.2177(6) and 0.2488(5)cm−1 for the X (v=0), A (v=0 and 1) and B (v=0) states of HoF and 0.2355(32) and 0.2448(29)cm−1 for the X (v=0) and A (v=0) states of HoCl, respectively. The following quadrupole coupling constants were obtained for the above six states; eQq0(HoF)=−0.0874(67), −0.0586(44), −0.0579(56), −0.0840(64)cm−1 and eQq0(HoCl)=−0.082(11), −0.060(11)cm−1. Comparison with previously determined values for HoO and HoS show that the ground state magnetic hyperfine structure in HoF and HoCl is entirely due to the Ho 4f electron and is consistent with the ground state, X8, configuration of Ho+{4f10(5I8)6s2}X− (X=F,Cl). Calculations of the ground state magnetic, h(X8), and quadrupole, eQq0(X8) hyperfine parameters from atomic hyperfine parameters are found to be consistent with the observed values for both molecules.

Hyperfine structure and Stark effect in the [18.0] 4 − X3Φ4 transition of iridium hydride, IrH and [18.2] 4 − X3Φ4 transition of iridium deuteride, IrD

High resolution spectra of IrH and IrD, with full width at half maximum (FWHM) of ∼0.001cm−1, have shown well resolved hyperfine structure due to the nuclear spin, I=3/2, of 193Ir and 191Ir. Analysis of the hyperfine structure in the [18.2] 4−X3Φ4 transition of 193IrD and 191IrD yielded well defined magnetic and quadrupole Ir hyperfine parameters which showed that the ground X3Φ4 state originates predominantly from the two open-shell Ir(5dπ35dδ3) configuration with a significant contribution from the four open-shell Ir(5dσ5dπ35dδ36sσ) configuration. Examination of the Stark effect in the [18.0] 4−X3Φ4 transition of 193IrH yielded electric dipole moments of 1.23(1) D and 0.76(1) D for the ground and excited states, respectively. The hyperfine constants and the dipole moment of the ground state are seen to follow the trend shown by the isovalent molecules, CoF, CoH and IrF.

Laser spectroscopy of holmium monosulphide: Hyperfine structure in the A[14.79]8.5, X18.5, X27.5 and W17.5 states

Laser induced fluorescence spectra, using a single frequency ring dye laser, have shown hyperfine structure in transitions from the A[14.79]8.5 state of HoS to three low-lying electronic states, X18.5, X27.5 and W17.5. Analysis of the hyperfine structure yielded magnetic hyperfine parameters, h(X1)=0.3298(27)cm−1, h(X2)=0.1124(29)cm−1, h(W1)=0.275(5)cm−1 and h(A)=0.2314(25)cm−1. The three low lying states originate from the ground Ho2+{4f10(5I8)6s}S2− configuration and the hyperfine parameters were used to determine the free Ho2+ ion quantum numbers appropriate to each state as well as the approximate relative contributions of the 4f and 6s electrons to the overall hyperfine energy. Calculation of the ground state magnetic hyperfine parameter h(X18.5) from atomic hyperfine parameters was found to be consistent with the observed values.

Mössbauer Study of the Ferroelectric State in Ga-Substituted CuFeO2

57Fe Mossbauer spectroscopic measurements have been conducted on CuFe1−xGaxO2 single crystals, in order to investigate the magnetic structures and hyperfine parameters in ferroelectric CuFe0.965Ga0.035O2 and paraelectric CuFeO2. We confirmed that the Mossbauer spectrum at 4.2 K in CuFeO2 is explained by the collinear antiferromagnetic structure with spins along the hexagonal c-axis. In the ferroelectric phase in CuFe0.965Ga0.035O2, the spectrum consists of three magnetic components, where magnetic hyperfine fields distribute in three different directions within the (110) plane. This configuration is not completely consistent with a simple proper screw structure with a uniform spin distribution. The quadrupole coupling constants e2qQ/2 are unexpectedly large for both specimens. In the ferroelectric state in CuFe0.965Ga0.035O2, e2qQ/2 becomes noticeably smaller than that in the paraelectric phase in CuFeO2. We discuss the difference in quadrupole coupling constant between the ferroelectric and paraelectric ...

The electric dipole moment of cobalt monoxide, CoO

A number of low-rotational lines of the E(4)Δ7/2 ← X(4)Δ7/2 (1,0) band system of cobalt monoxide, CoO, were recorded field free and in the presence of a static electric field. The magnetic hyperfine parameter, h7/2, and the electron quadrupole parameter, eQq0, for the E(4)Δ7/2(υ = 1) state were optimized from the analysis of the field-free spectrum. The permanent electric dipole moment, μ(→)(el), for the X(4)Δ7/2 (υ = 0) and E(4)Δ7/2 (υ = 1) states were determined to be 4.18 ± 0.05 D and 3.28 ± 0.05 D, respectively, from the analysis of the observed Stark spectra of F' = 7 ← F″ = 6 branch feature in the Q(7/2) line and the F' = 8 ← F″ = 7 branch feature in the R(7/2) line. The measured dipole moments of CoO are compared to those from theoretical predictions and the trend across the 3d-metal monoxide series discussed.

The hyperfine interaction in the odd isotope of ytterbium fluoride, 171YbF

The pure rotational spectrum of a minor isotopologue of ytterbium fluoride, 171YbF, in the X2Σ+ (v=0) state has been recorded using Fourier transform microwave (FTMW) spectroscopy and pump/probe microwave optical double resonance (PPMODR) spectroscopy. The pure rotational spectra and precisely measured splittings in the (0,0) A2Π1/2←X2Σ+ band were analyzed to produce an improved set of fine and magnetic hyperfine parameters for the X2Σ+ (v=0) state of 171YbF. A comparison with theoretical predictions is made.

Analysis of hyperfine structure in the 0–0 band of the [17.6]2.5–X2.5 transition of iridium monoxide, IrO

Laser induced fluorescence spectra of the [17.6]2.5–X2.5 0–0 band of iridium monoxide, IrO, have been obtained at high resolution (<40MHz). The hyperfine structure due to 193Ir (I=3/2) and 191Ir (I=3/2) is well resolved enabling determination of magnetic (h5/2) and nuclear electric quadrupole (eQq0) hyperfine parameters for the [17.6]2.5 (v=0) and X2.5 (v=0) states. The dominant configuration of the ground state is determined by comparing the observed molecular hyperfine parameters with values calculated for several possible ground state configurations using atomic hyperfine parameters. A perturbation calculation suggests that the X2.5 state results from the mixing of the Ω=5/2 component of the predicted ground 4Δi state with the Ω=5/2 components of two low-lying excited 2Δi states.

Molecular hyperfine parameters in the 1 3Σ u + and 1 3Σ g + states of Li2, Na2, K2 and Rb2

Magnetic hyperfine parameters have been computed for the 1 3 Σ + and 1 3 Σ + states of Li2 ,Na2 ,K2 and Rb2. The parameters were computed with MCSCF wavefunctions and the calculations were repeated for a series of internuclear distances. The results are compared with a recent observation of the hyperfine structure in Rb2, and to the atomic hyperfine parameters. The available empirical data are reproduced with high accuracy. For the present systems, the molecular hyperfine parameters are largely determined by the corresponding atomic hyperfine interactions. The computed molecular parameters at the dissociation limit deviate at most 11% from the experimentally determined atomic ones.

Effect of Vacancies on Positron Annihilation and Hyperfine Interactions in Fe-Al Alloys - &lt;i&gt;Ab Initio&lt;/i&gt; Study

Vacancies occupying different sub-lattices of D03 structure of Fe3Al alloy were investigated by the full potential linearized augmented plane wave method. The calculations basing on the super-cell approach have been performed for the vacancy concentrations of 1.6 and 3 at.%. For both concentrations the sub-lattice preference for vacancy location was determined. The dependence of vacancy formation energy on magnetic state of structure has been found. The positron lifetimes for the annihilation in the bulk (Fe3Al) and in vacancies have been investigated basing on the ab initio results for the electron density. The effect of vacancies on spin magnetic moment and hy-perfine parameters of Fe atoms neighboring the vacancy was examined. The results are discussed and compared with the data available.