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365.
A. Cappelli R. Tuffi K. Schwertassek K. Czapla J. Plail E. Freedman H. Nechamkin R. Gerber K. Lathrop H. Rath O. Mecheels J. W. Groß E. v. Roll K. Heidler S. G. Barker B. A. Ryberg W. I. Tepnin P. M. Heertjes H. Anton F. Riecke W. Sserdjukow N. A. Juschkow 《Analytical and bioanalytical chemistry》1944,127(1):155-156
366.
The magnetic and electrical measurements carried out on the R2WO6 tungstates showed a paramagnetic behaviour for samples with R=Nd, Gd, Dy and Ho and more complex one for samples with R=Sm and Eu in the temperature range 4.2-280 K and an insulating state at room temperature. With increasing atomic number of the R element the Curie-Weiss temperature increases from −43.5 K for Nd2WO6 to −2.7 K for Ho2WO6, excluding Sm2WO6 and Eu2WO6 compounds for that the Curie-Weiss region is not observed and the imaginary part of susceptibility is close to zero. The effective magnetic moment is close to the theoretical one for the free R ion and the magnetic moment measured in magnetic field of 14 T and at temperature of 4.2 K, generally, does not reach the saturation state. The temperature independent residual susceptibility is negative for Nd2WO6 and positive for the remaining compounds suggesting different proportions of the Landau, Pauli and van Vleck contributions to the total susceptibility. An increase of the orbital magnetic contribution to the total magnetic moment is suggested from the fitting of the Landé factor in the compounds under study. 相似文献
367.
Steady-state conjugate natural convection in a square cavity filled with a porous medium is studied numerically in this paper.
The enclosure consists of two horizontal conductive walls of finite thickness and two vertical walls at different uniform
temperatures. The focus is on the role of solid-fluid conductivity ratio, k, on the flow and heat transfer characteristics and the average Nusselt number, , over the vertical hot and cold walls of the cavity for a limited set of particular parameters. It was shown that the interface
temperature, θw, along the top of the solid wall decreases with the increase in the wall conductivity k. Also, the values of decreases with the increase of the values of the parameter k. Comparison with known results from the open literature when the wall thickness of the horizontal solid walls is neglected
(non-conjugate problem) is excellent.
Received on 4 April 2000 相似文献
368.
T. Groń E. Malicka A.W. Pacyna R. Sitko 《Journal of Physics and Chemistry of Solids》2009,70(8):1175-1180
The magnetic and electrical properties of the Al-doped polycrystalline spinels ZnxCryAlzSe4 (0.13≤z≤0.55) with the antiferromagnetic (AFM) order and semiconducting behavior were investigated. A complex antiferromagnetic structure below a Néel temperature TN≈23 K for the samples with z up to 0.4 contrasting with the strong ferromagnetic (FM) interactions evidenced by a large positive Curie-Weiss temperature θCW decreasing from 62.2 K for z=0.13 to 37.5 K for z=0.55 was observed. Detailed investigations revealed a divergence between the zero-field-cooling (ZFC) and field-cooling (FC) susceptibilities at temperature less than TN suggesting bond frustration due to competing ferromagnetic and antiferromagnetic exchange interactions in the compositional range 0.13≤z≤0.4. Meanwhile, for z=0.55 a spin-glass-like behavior of cluster type with randomly oriented magnetic moments is observed as the ZFC-FC splitting goes up to the freezing temperature Tf=11.5 K and the critical fields connected both with a transformation of the antiferromagnetic spin spiral via conical magnetic structure into ferromagnetic phase disappear. 相似文献
369.
Magnetization and susceptibility were investigated as a function of temperature and magnetic field in polycrystalline Mn[Cr0.5Ga1.5]S4 spinel. The dc susceptibility measurements at 919 Oe showed a disordered ferrimagnetic behaviour with a Curie-Weiss temperature θCW=−55 K and an effective magnetic moment of 5.96 μB close to the spin-only value of 6.52 μB for Cr3+ and Mn2+ ions in the 3d3 and 3d5 configurations, respectively. The magnetization measured at 100 Oe revealed the multiple magnetic transitions with a sharp maximum at the Néel temperature TN=3.9 K, a minimum at the Yafet-Kittel temperature TYK=5 K, a broad maximum at the freezing temperature Tf=7.9 K, and an inflection point at the Curie temperature TC=48 K indicating a transition to paramagnetic phase. A large splitting between the zero-field-cooled (ZFC) and field-cooled (FC) magnetizations at a temperature smaller than TC suggests the presence of spin-glass-like behaviour. This behaviour is considered in a framework of competing interactions between the antiferromagnetic ordering of the A(Mn) sublattice and the ferromagnetic ordering of the B(Cr) sublattice. 相似文献
370.
There has recently been a growing interest in dye sensitized solar cells (DSSCs) based on ruthenium metal, but due to the scarcity and high price of ruthenium, design of better and cheaper light adsorbent dyes based on more abundant metal ions is one of the key issues for future development of the DSSCs. Using density functional theory (DFT) and time-dependent DFT we have studied the properties of new and abundant metal ion-based polypyridyl dyes for p-type DSSCs and compared with ruthenium and other scarce metal ions. Molecular geometries, electronic structures, and optical absorption spectra have been calculated using an implicit solvent corresponding to acetonitrile. The calculated fair light harvesting efficiency, high hole injection efficiency and Gibbs free energy for the hole injection and longer excited state lifetime (important for reflecting the efficiency of solar cells) for the new abundant metal ions (V3+ and Cr2+) based dyes could provide promising sensitizers for efficient next generation DSSC's for p-SC. 相似文献