N. Büttgen

Spin and orbital frustration in MnSc2S4 and FeSc2S4.

Crystal structure, magnetic susceptibility, and specific heat were measured in the normal cubic spinel compounds MnSc2S4 and FeSc2S4. Down to the lowest temperatures, both compounds remain cubic and reveal strong magnetic frustration. Specifically the Fe compound is characterized by a Curie-Weiss (CW) temperature ThetaCW = -45 K and does not show any indications of order down to 50 mK. In addition, the Jahn-Teller ion Fe2+ is orbitally frustrated. Hence, FeSc2S4 belongs to the rare class of spin-orbital liquids. MnSc2S4 is a spin liquid for temperatures T>TN approximately 2 K.

Switching the ferroelectric polarization in theS=1∕2chain cuprateLiCuVO4by external magnetic fields

We present a detailed study of complex dielectric constant and ferroelectric polarization in multiferroic LiCuVO4 as function of temperature and external magnetic field. In zero external magnetic field, spiral spin order with an ab helix and a propagation vector along the crystallographic b direction is established, which induces ferroelectric order with spontaneous polarization parallel to a. The direction of the helix can be reoriented by an external magnetic field and allows switching of the spontaneous polarization. We find a strong dependence of the absolute value of the polarization for different orientations of the spiral plane. Above 7.5 T, LiCuVO4 reveals collinear spin order and remains paraelectric for all field directions. Thus this system is ideally suited to check the symmetry relations for spiral magnets as predicted theoretically. The strong coupling of ferroelectric and magnetic order is documented and the complex (B,T) phase diagram is fully explored.

Interplay between localized and itinerant magnetism in Co-substituted FeGa3

The evolution of the electronic structure and magnetic properties with Co substitution for Fe in the solid solution Fe

Spin-modulated quasi-one-dimensional antiferromagnet LiCuVO4

_{1-x}

Search for a spin-nematic phase in the quasi-one-dimensional frustrated magnet LiCuVO 4

Co

Heavy fermions in LiV2O4: Kondo compensation versus geometric frustration

_x

NMR study of the high-field magnetic phase of LiCuVO 4

Ga

Magnetic structure of the frustrated S = 1/2 chain magnet LiCu2O2 doped with nonmagnetic Zn

_3

High-field NMR of the quasi-one-dimensional antiferromagnet LiCuVO4

was studied by means of electrical resistivity, magnetization, ab-initio band structure calculations, and nuclear spin-lattice relaxation

Magnetic correlations in frustrated LiV2O4 and ZnV2O4

1/T_1