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The magnetic excitation spectrum in the two-dimensional (2D) S = 1/2 Heisenberg antiferromagnet copper deuteroformate tetradeuterate has been measured for temperatures up to T similar to J/2, where J = 6.31 +/- 0.02 meV is the 2D exchange coupling. For T < ...
Driven by antiferromagnetic quantum fluctuations on a deformable lattice, spin-Peierls systems dimerize magnetically and structurally at low temperatures. In this dimer phase all excitations with non-zero magnetization have a finite energy. The energy gain ...
Med lukningen af DR3-reaktoren på Risø mister Danmark sit eneste virkeligt store forskningsanlæg, som gennem fire årtier har sat dansk fysik og materialeforskning på verdenskortet. Danske, svenske og norske forskere forsøger nu at skaffe en større og mere ...
The incommensurate magnetic soliton lattice in the high-field phase of a spin-Peierls system results from quantum fluctuations. We have used neutron scattering techniques to study CuGeO3, allowing us to obtain the first complete characterization of the exc ...
The correlations and fluctuations in Cu(DCOO)(2). 4D(2)O, which is a good physical realization of the 2D S = 1/2 Heisenberg antiferromagnet on a square lattice, have been measured by neutron scattering measurements. The quantum fluctuations cause a non-uni ...
Quadrupolar ordering in a 5f electron system has been observed directly for the first time, using x-ray scattering techniques. In UPd3 at low temperatures satellite peaks appear at (1, 0, l) (orthorhombic notation) with I odd and even. Both sets of peaks s ...
CuGeO3 undergoes a transition from a spin-Peierls phase to an incommensurate phase at a critical field of H-c approximate to 12.5 T. In the high-field phase a lattice of solitons forms, with both structural and magnetic components, and these have been stud ...
The acoustic phonon dispersion curves of the hexagonal perovskite CsNiCl3 were measured at room temperature in the vicinity of the Gamma-point along the [0 0 1] and [1 1 0] directions. The derived velocity of sound values for the longitudinal and transvers ...
CuGeO3 is a good realization of a spin-Peierls system. Using neutron scattering, we have investigated the transition from the dimerized spin-Peierls phase to an incommensurately modulated high-field phase. The incommensurate period has been measured for fi ...
The study of \emph{quantum magnetism} remains at the forefront of condensed matter physics. Spin models provide a large class of many-body systems, in which cooperative quantum phenomena can be studied in a controlled way. In addition, the \emph{neutron sc ...
