Mingzhi Jin

Effect of high pressure on Mossbauer spectra of NiFe2O4 ultrafine particles with different grain sizes

The nickel ferrite ultrafine powders with different grain sizes (8, 12, 20, 40 and 80 nm) have been synthesized. Mossbauer spectra of Fe-57 nucleus in the samples composed of the nickel ferrite ultrafine powder before and after the high pressure treatments have been measured. The superparamagnetic relaxation is markedly suppressed by high pressure. The intensity of the sextets in Mossbauer spectra increases with increasing the grain size or pressure. The effect of high pressure on Mossbauer spectra of the samples may involve not only the physical changes, but also the chemical or structural ones in the ultrafine particles during the high pressure treatment, such as the formation of the interfacial region between the ultrafine particles and the rearrangements of the atoms in the surface layers of the ultrafine particles

Mössbauer spectroscopic study on nanocrystalline LaFeO3 materials

Perovskite-type nanocrystalline materials LaFeO3 with different crystal size were synthesized. These samples with different compacted pressure were investigated by Mössbauer spectroscopy at room temperature. The results showed that the LaFeO3 crystal in size of 70nm possessed an antiferromagnetic structure, that of 12nm was the superposition of the weaker antiferromagnetic structure and the stronger superparamagnetic structure. The rate of interface atoms to crystal atoms and the hyperfine field in nanocrystals varied with the compacted pressure.

Mössbauer Study of the Early Stages of Aging in 18Ni(350) Maraging Steel

Abstract The early stages of aging at 773 K in 18Ni(350) maraging steel were studied by Mossbauer spectroscopy. The experimental results showed that Fe-Co rich zones and Ni-Mo-Ti zones formed at the early stages of aging. The redistribution of atoms is fast at the initial stages of aging and then slows down. Intermetallic compounds were found to precipitate on the Ni-Mo-Ti zones.

Electric field gradient at the Eu nucleus in EuBa2Cu3O7−x around the superconducting transition temperature

Abstract In Mossbauer effect studies of the superconductor EuBa 2 Cu 3 O 7− x an appreciable anomaly around the superconducting transition temperature in the variation of both the electric quadrupole splitting of the 151 Eu nucleus and the asymmetry parameter of the electric field gradient has been observed. The change in the electric field gradient components and the possible structural and electronic rearrangement in the Cu-O layers in the crystal in the process of superconducting transition is discussed.

CALCULATIONS OF THE EIGENVALUES OF PURE QUADRUPOLE INTERACTION IN MOSSBAUER-EFFECT STUDIES

SummaryTwo approximate formulae to calculate the eigenvalues of pure quadrupole interaction in Mössbauer effect studies have been proposed and the eigenvalue coefficients in the formulae have been given for various excited states and ground states of the nucleus with different spin. All the eigenvalues of pure quadrupole interaction between both excited state and ground state of nucleus with spinI=3/2÷9/2 and the electric-field gradient with different asymmetry parameter (η=0÷1.0) have been calculated by these formulae. The results show that the accuracies in all the calculations are more satisfactory or same in comparison with those obtained by the formula of Shenoy and Dunlap, especially when the asymmetry parameter of electric-field gradient is larger than 0.8 for the nucleus with spinI=5/2.

Mössbauer spectra of 57Fe in a thick film of YBa2(Cu0.97Fe0.03)3O7 - X irradiated by a large dose of γ-rays

Mossbauer spectra of Fe-57 in a thick film YBa2(Cu0.97Fe0.03)(3)O7-x irradiated by a large dose of gamma-rays from Co-60 have been measured. The variation of the relative intensities of some subspectra of Fe-57 in the. Mossbauer spectra of the thick film YBa2(Cu0.97Fe0.03)(3)O7-x after irradiation can be observed. This variation indicates that the change of the coordination environment around some Fe atoms in the lattice occurs due to irradiation. The relative intensity of subspectrum D1(Fe) at the Cu(1) site decreases and that of subspectrum D4(Fe) at the Cu(1) site increases. This may be because of the possible oxygen atom hopping between the coordination environments of D1(Fe) and D4(Fe) in the lattice caused by irradiation. The effect of irradiation on the coordination environment around the Fe atom at the Cu(2) site is not appreciable

An X-ray diffraction and Mössbauer spectroscopic study on thec-axis texture YBa2(Cu1−x Fe x )3O7−y thick films

YBa2(Cu1−xFex)3O7−y thick films (x=0, 0.01, 0.02, 0.03) on ceramic substrate were prepared. X-ray diffraction determinations show the formation of partialc-axis texture perpendicular to the surface of the ceramic substrate in the preparation process. The57Fe Mössbauer spectra were measured at 300 K, where the angleθ between the incidenceγ-ray beam and the surface of the film is 90° and 36°, respectively. The57Fe Mössbauer spectra withθ=90° possess four sets of asymmetrical doublets.

Mössbauer effect studies on some bioinorganic complexes of europium.

The bioinorganic complexes of europium with N-acetyl-DL-alanine, N-acetyl-DL-valine, and DL-alanyl-DL-alanine have been synthesized and the Mössbauer spectra at room temperature have been measured for these solid state complexes. The Mössbauer parameters indicate that the water molecules in these complexes are not directly linked to the central europium ion and are outside the coordination sphere of europium and biological ligands, and that the chemical bond between the europium ion and the ligands may be predominantly ionic in character, with the possibility of partial covalent contribution.

151Eu and57Fe Mössbauer effect studies of magnetic interactions in europium transition element oxides solution

The solid state solutions of europium transition element oxides Eu (Fe0.8M0.2)O3 (M=Sc,Cr,Mn,Co) are synthesized. The X-ray diffraction of the compound shows that all the compounds possess the perovskite structures. Both the151Eu Mössbauer spectra and the57Fe Mössbauer spectra are measured. The hyperfine magnetic field and non-axisymmetric electric field gradient are observed in the151Eu Mössbauer spectrum. The57Fe Mössbauer spectrum shows that there are four components of hyperfine fields corresponding to four kinds of different neighbours of the Fe ion.

OBSERVATION OF MOSSBAUER-EFFECT IN THE HIGH-TEMPERATURE SUPERCONDUCTOR EUBA2CU3O7-X WITH DC ELECTRIC-CURRENT

The difference between the Mossbauer parameters for EuBa2Cu3O7-x with dc electric current and those without dc electric current at 83 K has been observed. The change in isomer shift, electric quadrupole splitting and the asymmetry parameter of the electric field gradient at the Eu-151 nucleus may be caused by the movement of a mass of conduction electrons along a certain direction in the EuBa2Cu3O7-x crystal with a layered structure.