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991.
992.
E. Papirer E. Walter A. Vidal E. Held 《Journal of magnetism and magnetic materials》1993,120(1-3):53-57
The surface properties of needle-shaped iron pigments for magnetic recording media have been determined by inverse gas chromatography. It is shown that the outer passivating layer is responsible for the physical adsorption characteristics of the pigments. 相似文献
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994.
H. Drößler H.-D. Jostarndt J. Harnischmacher J. Kalenborn U. Walter A. Severing W. Schlabitz E. Holland-Moritz 《Zeitschrift für Physik B Condensed Matter》1996,100(1):1-11
The antiferromagnetic ordering temperatures of the rare earth (RE) moments in RE Ba2 Cu3O7-gd, obtained from specific heat measurements, are roughly in agreement with the de Gennes factors, i.e., the ordering mechanism can be mainly seen as an indirect spin-spin exchange. However, the oxygen dependence of T N is found to be reversed for the light rare earths compared to the heavy rare earths. As origin for this systematic observation an indirect interaction between the 3d-moments of copper and the 4f-moments of rare earths is discussed as a second order effect. Such an interaction is supported by measurements of the 4f relaxation behavior on the Nd 1: 2: 3 cuprates by inelastic magnetic neutron scattering. Here, the usual thermally driven increase of the magnetic relaxation rate is suppressed up to about 80 K. This correlates with the appearance of a spin gap found by Rossat- Mignod in YBa2Cu3O7 and therefore the 3d-4f coupling can be understood as an interaction of the 4f moments with a spin-fluctuation exchange in the CuO2 planes. Furthermore, the quasielastic magnetic response has a Gaussian contribution at temperatures below 100 K, i.e., much above the long ranged ordering temperatures T N. Magnon-like excitations appear already at slightly larger temperatures than T N. In addition the paramagnetic inelastic spectra show only little dependence of the crystal field scheme on the oxygen concentration. 相似文献
995.
Synthesis and Crystal Structure Determination of Dimethyldi-(N-Methylimidazolium)silicon Bromide The reaction of dibromodimethylsilane with n-methylimidazole (NMI) leads to a 1:2 compound stable at room temperature. The reaction was carried out at room temperature and colorless, moisture sensitive crystals were obtained by sublimation. The addition compound crystallizes in the orthorhombic space group Pcam (No. 57) with lattice constants a = 1 110 96(8) pm, b = 1 142.3(2) pm and c = 1 238.9(3) pm. For 1 317 independent reflections, measured at 21°C, the structure could be refined to R = 0.040 and Rw = 0.041. 相似文献
996.
Formation of cyclic Amidiniumiodides and -polyiodides from 1,3,5-Trimethyl-hexahydro-1,3,5-triazine and Iodine The reaction of 1,3,5-trimethyl-hexahydro-1,3,5-triazine (CH3NCH2)3 with iodine in the molar ratio (CH3NCH2)3:I2 = 2:1 gives the new compound 1,3,5-trimethyl-tetrahydro-1,3,5-triazinium-iodide C6H14N3I. This iodide adds one mole I2 and forms 1,3,5-trimethyl-tetrahydro-1,3,5-triazinium-triiodide C6H14N3I3. The crystal structure analysis shows a cation, in which two methyl groups and five ring atoms are planar arranged. The third methyl group stands axial to the ring. 1,3,5-Trimethyl-tetrahydro-1,3,5-triazinium-pentaiodide is formed by adding a further mole I2. 相似文献
997.
Walter Alexandre Carnielli Carlos Augusto Di Prisco 《Mathematical Logic Quarterly》1993,39(1):461-474
Several types of polarized partition relations are considered. In particular we deal with partitions defined on cartesian products of more than two factors. MSC: 03E05. 相似文献
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