Crystal field effects in RERh4B4 compounds (RE = rare earth)

By analysis of a large body of available data, crystal field parameters have been obtained for compounds in the series RERh₄B₄ (RE = rare-earth). These parameters have then been used to calculate properties related to the electronic and magnetic properties of such compounds, and it is shown that a substantial unification of current information is obtained for properties including bulk magnetization (polycrystalline and single crystal), magnetic susceptibility, magnetic anisotropy, Schottky anomalies in the specific heat and suppression of the superconducting transition temperature due to magnetic impurities. In agreement with previous discussions crystal field effects are found to clarify the systematics of magnetic transition temperature, but not to give a full explanation. Other phenomena, such as discrepancies in the magnetic moment of ErRh₄B₄ as measured by neutron diffraction and by Mo¨ssbauer spectroscopy cannot be explained as crystal field related phenomena.     

The role of electrodynamic interactions on energy loss intensities of adsorbed molecules

The effect on energy loss intensities of the electrodynamic interactions with the substrate and neighboring adsorbed molecules is discussed. The experimentally observed large variations in the loss intensity from molecules adsorbed on various sites are considered. A simple dipole model of the molecule interacting with its image in the substrate and its neighbors on equivalent and inequivalent sites is used. Good agreement with experiment for a well characterized surface coverage of bridge and on-top bonded CO molecules on Ni(111) is found.     

关于n+k相多体系(k≥4)封闭网的构造

本文证明了n+k多体系(k≥4)的全部可能的封闭网均可以通过若干相应的子n+3相多体系的拼合运算得出,从而为具体构造n+k相多体系(k≥4)的全部合理的封闭网,提供了基本方法。     

超导临界温度理论(Ⅱ)

在文献[1]中,我们导出了超导临界温度T-c的一个严格级数表式.本文讨论这个级数的收敛范围,以及通过解析延拓来扩展收敛范围的可能性.结论是:我们的T_c级数(指文献[1]原来的级数,或者经过延拓后的级数)在∞>λ>λ₀的整个范围内,都是收敛的.这里λ₀是Matsubara表象中使决定T_c的方程具有正实数解的最小的λ值.它实际上就是库伦赝势.因此,也许除了少数非常弱耦合的超导体以外,我们的T_c级数能适用于一切超导体.     

An Fe Mössbauer effect study of metastable Al86Fe14prepared by rapid solidification

Icosahedral Al₈₆Fe₁₄ has been prepared by rapid quenching from the melt. Mössbauer effect spectra are quadrupole split doublets. The temperature dependence of the isomer shift is consistent with the second order doppler shift and the quadrupole splitting decreases linearly with temperature.     

Antiferromagnetism in57Co-doped La2CuO4−y studied by Mössbauer spectroscopy

Mössbauer effect studies of⁵⁷Co-doped La₂CuO_4?y were performed at temperatures between 4.2 K and room temperature. These confirm the antiferromagnetic ordering of these compounds below room temperature. Temperature dependence of the quadrupole splitting shows that the hyperfine field is at an angle with thec-axis.     

TDPAC and Mössbauer measurements of hyperfine fields in chromium-based chalcogenide spinels

Hyperfine magnetic fields are measured at Cd-111 and Sn-119 in CdCr₂Se₄ and CuCr₂Se₄, as well as at Cd-111 in CdCr₂S₄ and CuCr₂S₄. Quadrupole frequencies are measured for Cd-111 in CdCr₂S₄ and CdCrvSe₄ above T_c.     

Anisotropic hyperfine interactions and spin relaxation in neptunyl salts

Mössbauer spectra of hexavalent neptunyls X₂(NpO₂)Cl₄ and X₄(NpO₂)(CO₃)₃ with X=Na, K, Cs, (NH₄) and [C₂H₅)₄N] are discussed and compared to EPR data. In cases where reliable values of hyperfine parameters can be extracted, the Mössbauer spectra give fine details of bonding structure. It is found that the O–Np–O bond is not linear and that exchanging the cation results in small but definite changes.Work supported by the Bundesministerium für Forschung und Technologie and the U.S. Department of Energydeceased