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1.
A. Dönni P. Fischer A. Furrer P. Bonville F. Hulliger H. R. Ott 《Zeitschrift für Physik B Condensed Matter》1990,81(1):83-88
A polycrystalline smaple of nonstoichiometric ytterbium phosphide, YbP0.84, was investigated by neutron scattering, Mössbauer spectroscopy and bulk magnetic measurements. Neutron diffraction experiments prove the existence of antiferromagnetic type II ordering belowT
N
=0.64 K, in contrast to the observed antiferromagnetic type III ordering in the stoichiometric Kondo-like compounds YbN and YbAs. The temperature dependence of the average ordered magnetic moment per Yb3+ ion with saturation value Yb = 1.03(7)
B
is similar to that of YbN. Mössbauer experiments prove the magnetic phase transition to be first order with different regions in the sample having slightly different transition temperatures. By means of inelastic neutron scattering the crystal-field level scheme was established to be
6 –
8(19meV) –
7(43meV). 相似文献
2.
3.
The structure of GdPS is orthorhombic, space group Pmnb; a = 5.3620(5), b = 5.4079(6), c = 16.742(2)Å, Z = 8. It is a distorted derivative of the tetragonal PbFCl structure (a0, c0) with . The distortions are due to the formation of phosphorus chains. This structure type is found also in other rare-earth sulfopolyphosphides, e.g., with Ln = La···Sm, Tb···Tm, Y. 相似文献
4.
Re2Te5 crystallizes in a new structure type, having space group Pbca (No. 61) with a = 13.003(5), b = 12.935(7), c = 14.212(5) Å, Z = 12. All atoms are in the general positions 8(c), apart from one Te atom which occupies the special position 4(a) in a center of symmetry. The Re atoms are arranged in octahedral [Re6] clusters and all the atoms in general positions can be grouped as {[Re6Te8]Te6} complexes. The centers of these units and the Te atom in 4(a) are arranged like a slightly distorted rock salt structure. The Te atoms can be replaced by Se atoms up to at least 40%. Re2Te5 and Re2Se2Te3 reveal a semiconductor-like electric behavior which is accounted for by the chemical bonding. 相似文献
5.
O. Elsenhans P. Fischer A. Furrer K. N. Clausen H. G. Purwins F. Hulliger 《Zeitschrift für Physik B Condensed Matter》1991,82(1):61-75
Compared to previous bulk magnetic measurements unusual magnetic ordering phenomena were detected by systematic neutron scattering experiments performed in the temperature range of 7 mKT300 K on the series of cubic metallic compounds REPd3 of the rare earths RE=Nd, Tb, Dy, Er, Tm and Yb. Except for ErPd3 withT
N
=3 K the observed critical temperatures are compatible with the de Gennes scaling. The complexity of long-range magnetic ordering increases with decreasing 4f
n
occupancy, ranging from ferro- or ferrimagnetism in YbPd3 and DyPd3 via commensurate antiferromagnetic ordering in ErPd3 and TmPd3 [k=(1/2, 1/2, 0)] to incommensurate antiferromagnetic ordering of modulated type in TbPd3 and NdPd3. Both RKKY interactions, crystalline electric field, hybridization with 4d states of Pd as well as nuclear spin polarization in the case of RE=Nd appear to be of importance for the magnetic properties of REPd3 systems. 相似文献
6.
In the Gd monochalcogenides up to three different structural distortions have been detected in the magnetically ordered regime. Our experiments indicate that all three phases show type II antiferromagnetic order but with different orientations of the magnetic moments: A truly trigonal phase withm
k
k=[1/2, 1/2, 1/2], a monoclinic phase withabc, =/2+, and the spins oriented along [110], and a pseudo-rhombohedrally compressed monoclinic phase with the spins in the (111) planes. The spin flips can be accounted for by a model including anisotropic exchange interactions. 相似文献
7.
Muller T Hulliger J Seichter W Weber E Weber T Wubbenhorst M 《Chemistry (Weinheim an der Bergstrasse, Germany)》2000,6(1):54-61
A new type of dumb-bell-shaped host molecule (6-8) has been synthesised, of which 1,8-bis((1)-adamantyl)-1,3,5,7-octatetrayne (8 = BAOT) forms an open porous architecture when cocrystallised with a number of typical solvent molecules. Adamantyl substituents attached to a tetraalkyne spacer build up the walls of parallel channels wherein guest molecules are aligned. Surprisingly, the tetraalkyne unit is significantly bent. Desolvation experiments provide evidence for a reversible inclusion of guests. In the case of the inclusion of 2-butanone, a partial substitution by symmetrical and asymmetrical long-chain chromophores during crystallisation was possible. Stained crystals showed optical frequency doubling. The crystal structure analysis revealed a centric space group, although considerable translational and orientational disorder was present. Application of scanning pyroelectric microscopy revealed that the growth of inclusion compounds with 2-butanone produced polar ordering of guest molecules, which were aligned in two macro-domains of opposing polarity. The resulting orientation of the carbonyl dipoles is in agreement with the theoretical prediction of a Markov model of spontaneous polarity formation based on molecular recognition processes on growing crystal faces. The present case represents a new example of a property-driven supramolecular synthesis. 相似文献
8.
9.
The mechanism of insertion of p-nitroaniline (PNA) and its diffusion behavior in channels of the hexagonal host structure of tris(o-phenylenedioxy)cyclotriphosphazene (TPP) was investigated by means of molecular modeling tools. Strong preferential sites in the bulk were found to be due to pi-pi and NH-pi interactions between PNA and channel walls of TPP. MD simulations showed that diffusion can be characterized by jumps from one site to the next, occurring mainly because of the dynamic flexibility of the host structure. Calculations of host-guest interactions between the TPP surface and PNA approaching the entrance of channels with its terminal H2N-first or O2N-first revealed that the H2N-first insertion is clearly preferred. Preferential insertion of PNA is found to be the reason for polar effects, observed experimentally. Because of a distinct guest-host recognition at the surface, guest-guest interactions were found to have a minor influence on polarity. 相似文献
10.
Bond AD Griffiths J Rawson JM Hulliger J 《Chemical communications (Cambridge, England)》2001,(23):2488-2489
Non-centrosymmetric structures are promoted through the use of perfluoroaromatics containing structure-directing CN...X (X = Br, I) supramolecular synthons. 相似文献