Related papers: Response: Spin-Singlet clusters in the ladder comp…
The microscopic spin-spin correlations in the 2D layered spin-1 honeycomb lattice compound Na2Ni2TeO6 have been investigated by neutron diffraction and inelastic neutron scattering. The honeycomb lattice of spin-1 Ni2+ ions, within the…
Neutron scattering measurements on powder NaNiO2 reveal magnetic Bragg peaks and spin waves characteristic of strongly correlated s=1/2 magnetic moments arranged in ferromagnetic layers which are stacked antiferromagnetically. This…
The structure of Na0.5CoO2, the low temperature insulator that separates the magnetic and superconducting regions in the NaxCoO2.yH2O phase diagram, is studied by high resolution powder neutron diffraction at temperatures between 10 and 300…
The layered perovskite compound NaV_2O_5 exhibits charge ordering (CO) and spin gap formation which is driven by inter- site Coulomb forces and exchange dimerisation. Experimentally it was found that the CO transition is rapidly reduced by…
Electron pairing and ferromagnetism in various cluster geometries are studied with emphasis on tetrahedron and square pyramid under variation of interaction strength, electron doping and temperature. These exact calculations of charge and…
We have performed ab-initio calculations of the electronic structure and exchange couplings in the layered vanadates CaV2O5 and MgV2O5. Based on our results we provide a possible explanation of the unusual magnetic properties of these…
We present a unique study of the frustrated spinel MgV2O4 which possesses highly coupled spin, lattice and orbital degrees of freedom. Using large single-crystal and powder samples, we find a distortion from spinel at room temperature…
We investigate the temperature dependent optical properties of NaV2O5, in the energy range 4meV-4eV. The symmetry of the system is discussed on the basis of infrared phonon spectra. By analyzing the optically allowed phonons at temperatures…
We have performed measurements of the magnetic susceptibility of NaV$_2$O$_5$ between 2 and 400 K. The high temperature part is typical of spin 1/2 chains with a nearest--neighbour antiferromagnetic exchange integral $J$ of 529 K. We…
We investigate weakly coupled spin-1/2 ladders in a magnetic field. The work is motivated by recent experiments on the compound (C5H12N)2CuBr4 (BPCB). We use a combination of numerical and analytical methods, in particular the density…
Raman scattering in the quarter-filled spin ladder system alpha'-NaV_2O_5 shows in the dimerized singlet ground state ($T \leq T_{SP}=35K$) an unexpected sequence of three magnetic bound states. Our results suggest that the recently…
Recent X-ray analysis and NMR- experiments have shown that alpha'- NaV2O5 is not a conventional spin-Peierls (SP) compound because above the transition at 33K it is in a homogeneous mixed valent (MV) state and atomic spin chains do not…
We report high resolution polarized infrared studies of the quarter-filled spin ladder compound alpha'-NaV_2O_5 as a function of temperature (5K <= T <= 300K). Numerous new modes were detected below the temperature T_c=34K of the phase…
We present new experimental results of low temperature x-ray synchrotron diffraction, neutron scattering and very low temperature (mK-range) bulk measurements on the nanotube system ${\tube}$. The crystal structure determined from our data…
The nuclear spin-lattice relaxation rate (1/T1) at the V sites in CaV2O5 was measured. The result was compared with the calculation for the two-leg ladder with the strong-coupling expansion. We found a good agreement on the temperature and…
Band structure calculations within the local spin-density approximation are presented in order to investigate the electronic and magnetic properties of the zigzag spin-chain compound In$_2$VO$_5$. The essential structural feature of the…
We measured the variable temperature infrared response of the spin ladder candidate (DTTTF)2Cu(mnt)2 in order to distinguish between two competing ladder models, rectangular versus zigzag, proposed for this family of materials. The…
We investigate weakly coupled spin-1/2 ladders in a magnetic field. The work is motivated by recent experiments on the compound $\mathrm{(C_5H_{12}N)_2CuBr_4}$ (BPCB). We use a combination of numerical and analytical methods, in particular…
Quantum Monte Carlo (QMC) and density-matrix renormalization group (DMRG) methods are used to study the coupled spin-pseudospin Hamiltonian in one-dimension (1D) that models the charge-ordering instability of the anisotropic Hubbard ladder…
Single crystal X-ray diffraction measurements were performed on one-dimensional mixed valence vanadium bronze $\beta$-SrV$_6$O$_{15}$ in which a metal-insulator transition exists at 170 K. Above 170 K the P2$_1$/a structure with zigzag…