Rongchuan Liu

Mössbauer studies of57Fe in high-Tc superconductors YBa2 (Cu1−xFex)3O7

Various phenomena induced by iron cation substitution for copper in high-Tc superconductor are discussed. Fe cations are substituted for both Cu(1) and Cu(2) sites, but the substitution is preferentially taking place on Cu(1) chain sites atx<3%. The Fe cations at Cu(1) chain sites exhibit anisotropic vibration. Three different types of oxygen coordinations of Fe(1) cations are identified by the point-charge model. The calculation indicates that Fe3+ are present in tetrahedral, pyramidal, and distorted octahedral coordinations.

Investigation of some anomalous hemoglobins

We have studied some anomalous hemoglobins by Mössbauer spectroscopy. We found that there is a correspondence between the physical conditions of the respective patients and the additional components of the Mössbauer spectra found for their hemoglobins.

The surfactant influence on the surface magnetic properties of Fe3O4 microcrystals

Mössbauer measurements, electron microscopy and infrared spectroscopy, have been used for investigating the Fe3O4 microcrystals coated with different surfactants. The experimental results show that the surface condition of the system changes and the anisotropy energy constantK of Fe3O4 microcrystals increases effectively when the surfactants being added. The spin pinning effect on a sample surface was observed and the pinning depth and the pinning direction were estimated. Besides, it has been shown that the anisotropy energy constantK of the coated Fe3O4 has an abrupt change nearbyTv.

Fe-57 Mössbauer effect studies of some ancient Chinese pottery from xudun

Abstract18 Sherds (4500 B.C.–4000 B.C.) unearthed from different archaeological layers at the same place were studied by Mössbauer spectroscopy. The original firing atmosphere can be deduced from the ratio of the Fe2+ to Fe3+. By comparing the Mössbauer parameters of the original and the refired sherds, we can assess the original firing temperatures.

A Mössbauer investigation of SnO2 films with preferred orientation of crystallites

The textured SnO2 films with different thickness in the range of 600–11200Å prepared by chemical vapour deposition (CVD) have been characterized by using conversion electron Mössbauer spectroscopy (CEMS) couping with X-ray diffraction (XRD) and Auger electron spectroscopy (AES). The evidence for the existence of an interaction between SnO2 and glass substrate with the formation of a interface layer about 200Å thick has been discussed. SnO2 existing in polycrystalline state with preferred crystal face orientation is found as long as the SnO2 films are thick than 1800Å.

A Mössbauer study of an ancient pottery figure (Western-Han dynasty)

The grey pottery figure manufactured in the Western-Han Dynasty (175-118 B.C.) and the clay gathered from the same site of Beidongshan in Xuzhou have been studied by X-ray Diffraction(XRD). X-ray Fluorescence (XRF), and Mössbauer spectroscopy. They were simultaneously fired under the same conditions in different atmospheres at various temperature up to 1100°C. This study deals with the original firing atmosphere, original firing temperature and its provenance. The information mentioned above can be inferred from the method of the refiring pottery and the firing clay. The results of the original firing temperature deduced from both of them are in goodself agreement. It is found that the values of the Mössbauer parameters for the unrefired pottery figure are approximately the same as those for the clay fired at 950°C for five hours in a reduced atmosphere. The XRF analysis confirmed the locality of this pottery figure.

Mössbauer study of amorphous Nd−Fe−B films and their crystallization processes

Amorphous Nd−Fe−B films prepared by rf sputtering and their crystallization processes have been investigated by Mössbauer spectroscopy. A preferable alignment of the magnetization was observed in the amorphous film with a low hyperfine field of 173 kOe. With crystallization the average hyperfine field increases sharply, and the preferable alignment of the magnetization vanishes rapidly. The spectrum of the sample annealed at 750°C with coercivityHc=15.7 kOe shows that only Nd2Fe14B phase exists.

Mössbauer studies of hemoglobin of the patients with liver cancer and cirrhosis

Red blood cells (RBC) of the patients with primary liver cancer and with cirrhosis were investigated by using Mössbauer spectroscopy. Control measurements were carried out on RBC from normal adults. The Mössbauer spectra of normal RBC are composed of two doublets corresponding to deoxy-Hb and Oxy-Hb. Besides disappearance or a decrease of the doublets corresponding to deoxy-Hb, no additional peak was detected in the samples from the patients.

The effect of oxidized surface layers on the inner core of fine iron particles

Mössbauer measurements on fine iron particles with the size ranging from 150 to 350 Å with oxidized surface layer are carried out between 81 and 300K. The spectra consist of two components, a component due to metallic iron and a second component with a larger hyperfine field. The thickness of the oxide surface layer calculated from the area ratio of the subspectra is about 19 Å, and is independent of the average diameter of the particles. A slight enhancement of the hyperfine field of the iron core with a decrease of particle size has been observed. It results from the contribution of the atoms at the interface layer and the dipole interaction between the particles. The dipole interaction decreases owing to the effects of the oxide surface layer on the dipole field.

The exact Mössbauer recoilless fraction in fractals ATT≠0

In this paper a detailed calculation of the Mössbauer fraction for a general non-Euclidean dimensionality is given. The result shows that the contributions to the Mössbauer effect in fractals come from three possible types of transition.