Study Of Hyperfine Interactions Research Articles

Nuclear moments: recent developments

The author has for many years kept a watching brief on the experimental study of nuclear electro-magnetic moments. Accurate values of nuclear magnetic dipole and electric quadrupole moments are a major product and the life blood of hyperfine interaction studies and their manifold applications. This paper outlines recent changes in the type of moment measurements being undertaken and the effect of modern complex electronic configuration computation on the extracted moment values.

Structure of the Local Environment and Hyperfine Interactions of <sup>57</sup>Fe Probe Nuclei in AMnO<sub>3</sub> (A = Sc, In)

The results of a Mössbauer study of hyperfine interactions of 57Fe probe nuclei in isostructural hexagonal manganites h-ScMnO3 and h-InMnO3 are presented. The results of measurements of the Mössbauer spectra at T TN, as well as calculations of the parameters of the electric field gradient tensor at 57Fe nuclei, demonstrated different behavior of the probe iron ions in these isostructural systems, reflecting the difference in the processes of defect formation in their crystal lattices. On the contrary, measurements at T TN did not reveal any differences in the local magnetic structure of 57Fe probe atoms in these oxides.

The Creation of Complex Multi-Component Models of Mössbauer Spectra Based on the Example of a Study of Hyperfine Interactions in Quasi-Binary Alloys with the Laves Phase Structure

In this paper, we describe a method for creating new custom models of partial Mössbauer spectra based on the existing ones built into the SpectrRelax program without changing the program itself by writing code fragments in the built-in Lua programming language. The extension of the capabilities of the SpectrRelax program is demonstrated using the example of studying hyperfine interactions of 57Fe nuclei in quasibinary Tb(Fe0.8Al0.2)2 and Ho(Fe0.8Mn0.2)2 alloys with the C15 Laves phase structure. A model for processing the spectra, which simultaneously takes the composite and magnetic nonequivalence of the positions of Fe atoms in these alloys, has been created and used, which makes it possible to obtain new data about the orientation of the axis of the easiest magnetization, the anisotropy of the hyperfine magnetic field, and the effect of substitution of Al and Mn atoms for Fe atoms on hyperfine parameters of Mössbauer spectra.

The Creation of Complex Multi-Component Models of Mössbauer Spectra Based on the Example of a Study of Hyperfine Interactions in Quasi-Binary Alloys with the Laves Phase Structure

In this paper, we describe a method for creating new custom models of partial Mössbauer spectrabased on the existing ones built into the SpectrRelax program without changing the program itself by writing code fragments in the built-in Lua programming language. The extension of the capabilities of the SpectrRelaxprogram is demonstrated using the example of studying hyperfine interactions of 57Fe nuclei in quasibinary Tb(Fe0.8Al0.2)2 and Ho(Fe0.8Mn0.2)2 alloys with the C15 Laves phase structure. A model for processingthe spectra, which simultaneously takes the composite and magnetic nonequivalence of the positions of Fe atoms in these alloys, has been created and used, which makes it possible to obtain new data about the orientationof the axis of the easiest magnetization, the anisotropy of the hyperfine magnetic field, and the effect of substitution of Al and Mn atoms for Fe atoms on hyperfine parameters of Mössbauer spectra.

Study of Phase Transformations and Hyperfine Interactions in Fe3O4 and Fe3O4@Au Nanoparticles

The paper presents the results of a study of iron oxide nanoparticles obtained by chemical coprecipitation, coated (Fe3O4@Au) and not coated (Fe3O4) with gold, which were subjected to thermal annealing. To characterize the nanoparticles under study, scanning and transmission electron microscopy, X-ray diffraction, and Mössbauer spectroscopy on 57Fe nuclei were used, the combination of which made it possible to establish a sequence of phase transformations, changes in morphological and structural characteristics, as well as parameters of hyperfine interactions. During the studies, it was found that thermal annealing of nanoparticles leads to phase transformation processes in the following sequence: nonstoichiometric magnetite (Fe3-γO4) → maghemite (γ-Fe2O3) → hematite (α-Fe2O3), followed by structural ordering and coarsening of nanoparticles. It is shown that nanoparticles of nonstoichiometric magnetite with and without gold coating are in the superparamagnetic state with a slow relaxation rate. The magnetic anisotropy energy of nonstoichiometric magnetite is determined as a function of the annealing temperature. An estimate was made of the average size of the region of magnetic ordering of Fe atoms in nonstoichiometric magnetite, which is in good agreement with the data on the average sizes of nanoparticles determined by scanning electron microscopy.

Hyperfine interaction studies in the David Shirley group, 1960–1975. II. Perturbed angular correlations and Mössbauer effect

In addition to the low-temperature nuclear orientation studies discussed in Paper I, David Shirley's research group at Berkeley was renowned for other types of studies of the interaction of probe nuclei with their electromagnetic environment, particularly perturbed angular correlations and the Mössbauer effect. The present paper discusses these other fields of research into hyperfine interactions and gives examples of the contributions of the Shirley group toward elucidating these interactions.

Hyperfine interaction studies in the David Shirley group, 1960–1975. I. Low-temperature nuclear orientation

Under the leadership of David Shirley, the hyperfine interactions group at Berkeley became one of the world’s leading laboratories for its diversity of studies of the interaction between probe nuclei and their environment. One branch of those studies, low-temperature nuclear orientation, concerned the radioactive decays of nuclei whose spins were oriented in a variety of electromagnetic environments at temperatures in the mK range. In the years 1960–1975, this group did pioneering research that produced more than 50 papers in the field, and at least 16 graduate students completed their dissertation research. The present paper gives a brief introduction to the field of low-temperature nuclear orientation, summarizes the main accomplishments of the Shirley group, and discusses examples of the variety of results obtained in the group’s research. Paper II deals with other hyperfine interaction studies by the Shirley group.

Ab Initio Study of Fine and Hyperfine Interactions in Triplet POH.

Phosphorous-containing molecules have a great relevance in prebiotic chemistry in view of the fact that phosphorous is a fundamental constituent of biomolecules, such as RNA, DNA, and ATP. Its biogenic importance has led astrochemists to investigate the possibility that P-bearing species could have formed in the interstellar medium (ISM) and subsequently been delivered to early Earth by rocky bodies. However, only two P-bearing molecules have been detected so far in the ISM, with the chemistry of interstellar phosphorous remaining poorly understood. Here, in order to shed further light on P-carriers in space, we report a theoretical spectroscopic characterisation of the rotational spectrum of POH in its A ground electronic state. State-of-the-art coupled-cluster schemes have been employed to derive rotational constants, centrifugal distortion terms, and most of the fine and hyperfine interaction parameters, while the electron spin–spin dipolar coupling has been investigated using the multi-configuration self-consistent-field method. The computed spectroscopic parameters have been used to simulate the appearance of triplet POH rotational and ro-vibrational spectra in different conditions, from cold to warm environments, either in gas-phase experiments or in molecular clouds. Finally, we point out that the predicted hyperfine structures represent a key pattern for the recognition of POH in laboratory and interstellar spectra.

NMR study of magnetic structure and hyperfine interactions in the binary helimagnet FeP

We report a detailed study of the ground state helical magnetic structure in monophosphide FeP by means of ${}^{31}$P NMR spectroscopy. We show that the zero-field NMR spectrum of the polycrystalline sample provides strong evidence of an anisotropic distribution of local magnetic fields at the P site with substantially lower anharmonicity than that found at the Fe site by M\"{o}ssbauer spectroscopy. From field-sweep ${}^{31}$P NMR spectra we conclude that a continuous spin-reorientation transition occurs in an external magnetic field range of 4 - 7 T, which is also confirmed by specific-heat measurements. We observe two pairs of magnetically inequivalent phosphorus positions resulting in a pronounced four-peak structure of the single crystal ${}^{31}$P NMR spectra characteristic of an incommensurate helimagnetic ground state. We revealed a spatial redistribution of local fields at the P sites caused by Fe spin-reorientation transition in high fields and developed an effective approach to account for it. We demonstrate that all observed ${}^{31}$P spectra can be treated within a model of an isotropic helix of Fe magnetic moments in the ($ab$)-plane with a phase shift of 36$^{\circ}$ and 176$^{\circ}$ between Fe1-Fe3 (Fe2-Fe4) and Fe1-Fe2 (Fe3-Fe4) sites, respectively, in accordance with the neutron scattering data.

Relaxation parameters of water molecules coordinated with Gd(III) complexes and hybrid materials based on δ-FeOOH (100) nanoparticles: A theoretical study of hyperfine inter-actions for CAs in MRI

Cancer is a serious disease that afflicts and worries much of the population, which significantly affects all ages and socio-economic groups and one reason is the great difficulty of the initial diagnostic phase. Thus, magnetic resonance imaging (MRI) is an effective technique for detecting cancer (especially breast cancer), however, for a better visualization of the tissues it is necessary to use the Contrast Agents (CAs), which are paramagnetic compounds capable of increasing the longitudinal and transverse relaxation times (T1 and T2) of water molecules. The CAs are important to increase the rate of relaxation of water protons, the most commonly used CAs are Gd3+ complexes. Thus, in this work we propose two new hybridizing contrast agent, d-FeOOH(100).[Gd(DTPA)(H2O)]2- and δ-FeOOH (100).[Gd(DTPA-BMA)(H2O)], both compounds are capable of increasing both relaxation times T1 and T2. Theoretical results show that the hybrid compound considerably increases the hyperfine coupling constants 1H and 17O of water molecules. In this way, our results show that both hybrid compounds can be used as new contrast agents, thus replacing Gd3+ complexes.

Preparation of In-doped Y2O3 ceramics through a sol-gel process: Effects on the structural and electronic properties

The Pechini-type sol-gel (PSG) process has been used for the preparation of doped oxides due to its capability to overcome most of the difficulties that frequently occur by using other producing methods. In this work we analyze the case of samples of pure and In-doped yttria (Y2O3) prepared by the PSG process. We experimentally characterize the synthesized samples by x-ray diffraction, micro-Raman spectroscopy, electrochemical impedance spectroscopy (EIS), and time-differential perturbed γ-γ angular correlation (PAC) spectroscopy, and we compare these results with those obtained starting from commercial oxide powders. We found that the PSG process can be used to successfully produce doped yttria in the cubic phase, with the impurities substitutionally located at the cationic sites of the structure. By the proposed PSG route, the inclusion of impurities does not affect the particle size nor the resistivity. However, when we compare the PSG samples with other samples produced from commercial powder, we found that the first have lower resistivities at grain interiors. On the other hand, PAC spectroscopy in 111In(→111Cd)-doped yttria allows the study of the dynamic hyperfine interactions observed by the radioactive 111Cd impurity-probe, which can be used to “sense” the host electron availability near the impurities after the electron-capture decay of 111In. Differences between PAC spectra for PSG samples and the commercial powder suggest that the PSG process introduces additional donor defects into the yttria electronic structure, which is consistent with the lower resistivity observed in the PSG samples by EIS spectroscopy.

Correction to: Stability of monoclinic phase in pure and Gd-doped HfO2: a hyperfine interaction study

Due to technical constraints this article was published in volume 240:1 with erroneous article citation ID number 8 whereas this should have been 78 which is corrected as such. Springer Nature sincerely apologizes towards the author(s) for the inconvenience caused.

Stability of monoclinic phase in pure and Gd-doped HfO2: a hyperfine interaction study

The present Time Differential Perturbed γ-γ Angular Correlation (TDPAC) measurements in bulk HfO2 report, for the first time, the presence of three regular sites at ambient condition, apart from the stable monoclinic phase (m-HfO2). Also, the effects of Gd impurity (5 at%) on HfO2 crystal structure was investigated by PAC. In pure HfO2, apart from the monoclinic component (~76%), four other minor frequency components have been found at room temperature. To further investigate the origin of these minor frequency components, PAC measurement at 673 K was performed. At 673 K, population of two of the four minor components was enhanced at the expense of the m-HfO2 as the population of m-HfO2 reduces to ~58%. On doping with 5 at% Gd, the population of monoclinic site drastically reduced to ~10% while one of the minor components got enhanced to a large extent (68%). The enhancements of the three minor components, both by temperature or by Gd impurity, indicate that these are the regular phases of HfO2 and could therefore be attributed to three orthorhombic phases of HfO2. The fourth minor component (5–10%) with values of ωQ ~ 7 Mrad/s, η = 0 can be assigned to crystalline defect site.

Hyperfine interaction and electronic spin fluctuation study on Sr2−xLaxFeCoO6 ( x = 0, 1, 2) by high-resolution backscattering neutron spectroscopy

The study of hyperfine interaction by high-resolution inelastic neutron scattering is not very well known compared to the other competing techniques viz. NMR, M\"ossbauer, PACS etc. Also the study is limited mostly to magnetically ordered systems. Here we report such study on Sr$_{2-x}$La$_x$FeCoO$_6$ (x = 0, 1, 2) of which first (Sr$_2$FeCoO$_6$ with x = 0) has a canonical spin spin glass, the second (SrLaFeCoO$_6$ with x = 1) has a so-called magnetic glass and the third (La$_2$FeCoO$_6$ with x = 2) has a magnetically ordered ground state. Our present study revealed clear inelastic signal for SrLaFeCoO$_6$, possibly also inelastic signal for Sr$_2$FeCoO$_6$ below the spin freezing temperatures $T_{sf}$ but no inelastic signal at all for for the magnetically ordered La$_2$FeCoO$_6$ in the neutron scattering spectra. The broadened inelastic signals observed suggest hyperfine field distribution in the two disordered magnetic glassy systems and no signal for the third compound suggests no or very small hyperfine field at the Co nucleus due to Co electronic moment. For the two magnetic glassy system apart from the hyperfine signal due only to Co, we also observed electronic spin fluctuations probably from both Fe and Co electronic moments. \end{abstract}

Evidence of enhanced ferromagnetic nature and hyperfine interaction studies of Ce-Sm doped Co-Ni ferrite nanoparticles for microphone applications

We present the results of the structural, Magnetic and low temperature Mössbauer spectroscopy studies of Co0.5Ni0.5Fe2-(x+y)CexSmyO4 (where x,y = 0.0, 0.01, 0.015 and 0.02) which was prepared by the solution combustion route using mixture of glucose and urea as fuel. The prepared samples were subjected to X-Ray Diffractometer (XRD), Transmission Electron Spectroscopy (TEM), Vibrating Sample Magnetometry (VSM) and Mössbauer Spectroscopy at room temperature and low temperature (15 K) to understand the phase, structure and magnetic behavior of the samples. The results of XRD reveals the formation of a single phase spinel cubic structure with space group Fd3̅m. The crystallite sizes are found to be increasing with increasing Ce3+ and Sm3+ content. This is due to the fact that bigger ionic radii of Ce3+ and Sm3+ replace Fe3+ ions at B site. The lattice parameter is found to be increasing with the increasing Ce3+ and Sm3+ content due to increased internal strain upon doping. The TEM micrographs reveals that the particles almost appear as spherical and agglomerated. Magnetic measurements show that all the obtained samples exhibit higher saturation magnetization (MS), remanence (Mr), coercivity (HC), anisotropy constant (K) and magneton number (ηB). This is due to the increase in A-B super exchange interaction in the samples. Further the increase in HC with the dopant concentration is interpreted as the enhanced magnetic pinning and ferromagnetic behavior in the samples. The room temperature Mössbauer spectra consist of broadened magnetic sextet and paramagnetic quadrupole-split lines. The presence of the magnetic sextet and doublet component on the Mössbauer spectra indicate the presence of superparamagnetic relaxation with a higher TB than the room temperature. The obtained results suggest that the rare earth doped Co-Ni ferrites are potential candidates for microphone applications.

Thermodynamic Properties, Mössbauer Study, and First-Principles Calculations of TlFe(MoO4)2

We report the results of magnetization and specific heat measurements, a 57Fe Mössbauer study of hyperfine interactions and density functional theory calculations in TlFe(MoO4)2 demonstrating two magnetic phase transitions at TN2 = 5.7 K and TN1 = 6.2 K. In the asymptotical critical region TN2 ≤ T ≤ TN1, the temperature dependence of the average hyperfine magnetic field ⟨Bhf(T)⟩ at the 57Fe nuclei is well-described by the power law ⟨Bhf(T)⟩ ∝ tβ with the static critical exponent β ≈ 0.37 inherent for a three-dimensional magnet. In this range, the Mössbauer spectra are described in terms of collinear spin-density-wave with the inclusion of high-order harmonics. The spectra of the low-temperature phase, below TN2, are well-fitted by a single six-line Zeeman pattern reflecting the equivalence of magnetic sites occupied by Fe3+ ions in an antiferromagnetic structure. The first-principles calculations allowed estimation of the strength of main exchange interactions.

Hyperfine interaction, Raman and magnetic study of YFeO3 nanocrystals

Glycine Nitrate Process (GNP) was used to obtain orthoferrites YFeO3 (YFO) nanoparticles. The structural phase formation of compound was confirmed by using XRD and Raman spectroscopy. Morphological, thermal, ferroelectric and magnetic properties at room temperature have been systematically studied via TEM, TG-DSC, Mossbauer, PE loop, and SQUID. Single phase YFeO3 nano-crystals with orthorhombic Pnma space group were successfully derived from GNP with average crystallite size 50–60 nm. The magnetic hysteresis loops indicates Fe spins orders antiferromagnetically with weak ferromagnetism due to the superexchange and Dzyaloshinski-Moriya (DM) antisymmetric exchange mechanism. The vibrational properties were characterized by Raman spectroscopy, in which 12 active modes were observed out of 24 Raman active modes. Spin-exchange striction is considered as a microscopic origin of ferroelectric polarization. The evidence for the ferroelectric character of the samples is observed in the saturation polarization loops at room temperature. Mossbauer spectra and XPS show that the Fe3+ is dominated in the compound.

Substitution driven reverse distorted FeO6 octahedral structure, magnetic properties and hyperfine interaction studies in Bi1-xLaxFeO3 powder

The Bi1-xLaxFeO3 (x = 0, 0.05, 0.10, and 0.15) powders were prepared by the hydrothermal method. The X-ray diffraction revealed an increase of lattice constants of the doped samples evidencing substitution of Bi by La ions. The morphology of the samples was investigated by the Scanning Electron Microscopy. The magnetic properties of the films were studied by vibrating sample magnetometry at room temperature. The evidence of reverse distorted FeO6 octahedral structure in the La doped samples was revealed by the Mössbauer spectra parameters: Is, Qs, H, Γ, χ2 and area ratio (A1/A2) of two-sextet.

Hyperfine interaction study of pressure induced phase transformations in Hafnia

Time Differential Perturbed Angular correlation (TDPAC) study of pressure dependent phase transition in HfO2 has been performed for the first time to reveal the change in local structure around Hf atom. The results show that the nuclear hyperfine interaction parameters namely, quadrupole interaction frequency and asymmetry parameter at atmospheric pressure are in agreement with literature while that at 45 GPa are significantly different from that at atmospheric pressure.

A comparative study of hyperfine interactions in Aurivillius compounds prepared by mechanical activation and solid-state sintering

Abstract X-ray diffraction and Mössbauer spectroscopy techniques were used to study the structure and hyperfine interactions of multiferroic Aurivillius compounds Bim+1Ti3Fem-3O3m+3. Samples were synthesized by two methods, that is, the solid-state sintering at various temperatures and mechanical activation in a high-energy ball mill. The compounds were obtained from a mixture of three polycrystalline powder oxides, that is, TiO2, Fe2O3 and Bi2O3. At room temperature, the Aurivillius compounds are paramagnetic materials with orthorhombic crystal structure. The c lattice parameter of the unit cell depends linearly on the m − number of layers with perovskite-like structure. Based on the Mössbauer studies, it is concluded that the hyperfine interactions parameters do not change with m number.