Milan Liu

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.

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.

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.

Mössbauer spectroscopic study on (Eu1−xGdx)FeO3

Europium gadolinium ferrites (Eu1−xGdx)FeO3 (X=0, 0.2, 0.4, 0.6, 0.8) are synthesized. The results of the X-ray diffraction show that all the compounds possess a perovskite structure. Both the151Eu Mössbauer spectra and the57Fe Mössbauer spectra are measured. The151Eu Mössbauer spectra are considered to be the pure quadrupole spectra. The results show that the isomer shift and the quadrupole splitting of the151Eu spectra vary with x. The hyperfine filed of the57Fe Mössbauer spectrum depends on the unit-cell volume. The57Fe spectra of the samples synthesised by the high-pressure and high-temperature mothod show a part of paramagnetic structure.

Mössbauer effect study of the magnetic state of iron atoms in Fe-Ni 36 wt.% Invar alloys

The57Fe Mössbauer spectra of the Fe-Ni 36 wt.% Invar alloy at different temperatures (300–530 K) have been measured. The experimental results indicate that the hyperfine field distributions are characterized by dual peaks. The temperature dependence of the hyperfine field indicates that some iron atoms may transfer from the ferromagnetic state to the antiferromagnetic one with increasing temperature, and that the variation of the ratio of numberN0 of the iron atoms in the antiferromagnetic state to the numberNh in the ferromagnetic state with temperature will obey the thermodynamic relationship.

RESEARCH ON THE THERMAL-DECOMPOSITION OF THE BIOINORGANIC COMPLEX OF EUROPIUM AND L-GLUTAMINE BY MOSSBAUER-SPECTROSCOPY

Abstract Mossbauer spectroscopy has been used to investigate the thermal decomposition of the bioinorganic complex of europium and l -glutamine. The Mossbauer parameters can demonstrate that the water molecules in the complex and the chlorine anion in the hydrogen chloride molecule, dissociated from the complex below 200°C, are not linked directly to the europium atom. The thermal decomposition process of the complex is discussed and a possible coordination model for the europium l -glutamine complex is also proposed on the basis of the thermogravimetric and derivative thermogravimetric curves, and from some evidence obtained from the Mossbauer effects of some decomposition products of the complex.

Mössbauer spectra of gadolinite and aeschynite

The Mössbauer spectra of the Natural gadolinite and aeschynite at 297K and 81K were measured. The Mössbauer spectrum of the gadolinite consists of one Fe3+ doublet and two Fe2+ doublets, and the multiple Fe2+ doublets in the spectrum of the gadolinite were relating to the next nearest neighbour effect. The Mössbauer spectrum of the aeschynite is composed of one Fe3+ doublet and one Fe2+ doublet, and this result is in agreement with crystal structure determination.

Iron distribution in chevkinite

In this paper Mössbauer spectra of chevkinite at 283K and 83K are presented for the first time. The spectra consist of two Fe2+ and two Fe3+ doublets, and the assignments were made according to the structure of chevkinite. Iron distribution obtained from the spectrum at 83 K is consistent with that at 283 K.