Zhang Pan-lin

The copper isotope effect in Ba2Y Cu3O7

Abstract The effect of isotopic substitution on the superconducting Tc in the 90 K superconductors Ba2Y Cu3O7 by replacing ordinary copper Cu with 63Cu and 65Cu has been studied. The transition temperatures are found to be the same within experimental error of ± 0.2K. This indicates that the copper isotope effect is absent in this material, as in the cases of oxygen.

EFFECT OF MANGANESE SUBSTITUTION IN R 2 AlFe 16-x Mn x (R=Y,Ho,Nd AND Pr)COMPOUNDS ON STRUCTURAL AND MAGNETIC PROPERTIES

The structural and magnetic properties of R2AlFe16-xMnx (0 ≤ x ≤ 8 for Y, Ho, 0 ≤ x ≤ 10 for Pr, 0 ≤ x ≤ 16 for Nd) compounds have been investigated by means of x-ray diffraction and magnetization measurements. The R2AlFe16-xMnx compounds have a hexagonal Th2Ni17-type structure for R = Y and Ho, and a rhombohedral Th2Zn17-type structure for Nd and Pr. With increasing x, the unit-cell volumes have a small increase initially, followed by a greater linear increase. The Curie temperature and the saturation magnetization of these compounds show marvelous drop with increasing x. Compensation point was observed in the temperature dependence of the magnetization for Ho2AlFe12Mn4 compound.

HIGH FREQUENCY MODES OF YBa 2 Cu 3 O 6+δ AND ITS VARLATIONS WITH OXYGEN CONTENT

在中国原子能科学研究院新建的宽角(～30°)Be过滤探测器中子非弹性散射谱仪上,在入射中子能量从10直至150meV的范围内,测量了几种不同氧含量的YBa 2 Cu 3 O 6+δ 样品的中子非弹性散射能谱。结果表明:(1)在δ=0和0.2时,在60至150meV能量范围内,发现有强的高频模存在,当其温度高到Nel点(～410K)以上直至466K时,没有观察出高频模强度的减弱。而δ=0.78和0.97时,在75至150meV能量范围内,散射强度在测量误在Si(100)衬底上用分子束外延在不同的温度下生长了不同组份的Ge x Si 1-x /Si应变层超晶格。用反射式高能电子衍射、X射线双晶衍射、卢瑟福背散射、透射电子显微镜以及Raman。散射等测试方法研究了Ge x Si 1-x /Si超晶格的生长及其结构特性。结果表明,对不同合金组份的超晶格,其最佳生长温度不同。x值小,生长温度高;反之,则要求生长温度低。对于x为0.1—0.6,在400—600℃的生长温度范围能够长成界面平整、

Magnetic properties of Dy2Fe17-xCrx and Er2Fe17-xCrx (x = 0-3) compounds

The crystal structure and magnetic properties of R2Fe17-xCrx (R = Dy, Er, 0 ≤ x ≤ 3) compounds have been investigated by means of x-ray diffraction and magnetization measurements. These compounds have hexagonal Th2Ni17-type structure. The unit-cell volumes decrease with the increase of Cr concentration x. The Curie temperature Tc of the Er2Fe17-xCrx compounds increases from 320 K for x = 0 to 403 K for x = 1.0 and then decreases with further increase of x. The Curie temperature Tc of Dy2Fe17-xCrx compounds increases from 364 K for x = 0 to 435 K for x = 1.0 and then decreases with further increase of x. The saturation magnetization of these compounds shows an approximately linear decrease with the increase of x. Spin reorientation transitions occurs in Er2Fe17-xCrx (x = 2.0 and 3.0).

Formation and magnetic properties of Dy2Fe17-x Mnx C(x = 0-17) prepared by arc-melting

We report on alloys formed by replacing iron with manganese in the compound Dy2Fe17C1.0. Samples were characterized by x-ray diffraction and magnetic measurements. The 2:17-type structure can be crystallized in the whole range of manganese substitution. The Curie temperature of the series of Dy2Fe17-xMnxC1.0(x = 0-17) drops down considerably from 515 K for x = 0 to about 20 K for compounds with high manganese concentration, and the compensation point was observed in a narrow range of x ≈ 4-6. The rapid decrease of the magnetization shows that the manganese substitution is not a simple magnetic dilution to the transition-metal sublattice moment, it indicates that the moment of Mn may be antiparallel to that of Fe. The field dependence of the magnetization of Dy2Fe17-xMnxC1.0 may indicate the existence of the nonlinear magnetic structure for the samples with high Mn concentrations.

Neutron-powder-diffraction study of the structure and magnetic properties of Nd2Fe14Si3

The crystal and magnetic structures of Nd2Fe14Si3 at room temperature were refined by Rietveld analysis of neutron-powder-diffraction data. It was found that silicon atoms occupy preferentially both 18 h and 18 f of Th2Zn17-type structure with occupancies 0.36 and 0.14, respectively. The Fe-Fe bond-lengths computed with the refined crystallographic parameters have optimum values, as compared with those of Nd2Fe17 compounds, which can explain well why the Curie temperature rises strongly when the unit cell volume reduces with the substitution of silicon for iron in Nd2Fe17.

NEUTRON-POWDER-DIFFRACTION STUDY OF ErFe 11.35 Nb 0.65 AND ErFe 11.35 Nb 0.65 N y

ErFe11.35Nb0.65 and ErFe11.35Nb0.65Ny have been synthesized and neutron-powder-diffraction experiments at room temperature performed. The ErFe11.35Nb0.65Ny nitride, obtained by gas-solid reaction, retains the ThMn12-type structure of its parent compound. The Nb atoms occupy 8i sites and the nitrogen atoms are located at 2b sites. The atomic magnetic moments of the Er ions are antiparallel to those of the Fe atoms. Upon nitrogenation, the lattice cell expands mainly along the a-axis and the atomic magnetic moments of Fe are enhanced.

A neutron powder diffraction study of the structure in Nd2Fe17Nx(x = 2.5, 3.0, 5.5)

The crystallographic and magnetic structures of Nd2Fe17Nx (x=2.5, 3.0, 5.5) at room temperature were refined by Rietveld analysis of neutron powder diffraction data. We found that Nd2Fe17Nx has a Th2Zn17 type structure (S. G. Rm) and the nitrogen atoms occupy both 9e and 18g sites simultaneously and at different rates.