Magnetism has been predicted to occur in systems where dipolar interactions dominate exchange. We present neutron scattering, specific heat and magnetic susceptibility data for LiErF 4 , establishing it as a model dipolar-coupled antiferromagnet with planar spin-anisotropy and a quantum phase transition 1

a b s t r a c tHigh quality centimeter size single crystals of Bi(Cu 1 À x Zn x ) 2 PO 6 (x ¼ 0%, 1%, 5%) have been successfully grown by the Travelling Solvent Floating Zone (TSFZ) technique. The crystals were grown with a rate of 1 mm/h in a gas mixture of 20% O 2 in Ar. Characterization of the single crystal samples by means of optical microscopy, X-ray powder diffraction, X-ray Laue diffraction, neutron diffraction and magnetization measurement are reported. The magnetic susceptibility w spin ðTÞ, measured from 2 to 300 K, passes a broad maximum around 60 K, followed by an exponential decrease towards lower T, and confirm the formation of a spin singlet ground state at low temperature. At low-temperature a paramagnetic Curie-like upturn quantitatively reflect the increasing Zn-doping level.

We present the experimental phase diagram of LiHo x Er 1-x F 4 , a dilution series of dipolar-coupled model magnets. The phase diagram was determined using a combination of ac susceptibility and neutron scattering. Three unique phases in addition to the Ising ferromagnet LiHoF 4 and the XY antiferromagnet LiErF 4 have been identified. Below x = 0.86, an embedded spin-glass phase is observed, where a spin glass exists within the ferromagnetic structure. Below x = 0.57, an Ising spin glass is observed consisting of frozen needlelike clusters. For x ∼ 0.3-0.1, an antiferromagnetically coupled spin glass occurs. A reduction of T C (x) for the ferromagnet is observed which disobeys the mean-field predictions that worked for LiHo x Y 1-x F 4 .

Millimeter-sized cobalt doped rutile crystals with a bi-pyramidal shape are obtained by chemical vapour transport using scroll-type H2Ti3O7 nanotubes as a precursor in which Co2+ ions are introduced by a simple ion exchange method prior to the growth. Despite the low concentration of Co2+ dopants (5 × 1019 cm−3), the resistivity of the single crystal shows a metallic behaviour above 50 K and the Seebeck coefficient has the signatures of polaronic quasiparticles. The magnetic properties of the material show a weak anti-ferromagnetic interaction between the spins on Co atoms below 50 K. This synthesis method could be beneficial for the growth of a large variety of doped TiO2 single crystals

a b s t r a c tLarge size high-quality Ca-doped Sr 14 À x Ca x Cu 24 O 41 (x ¼ 12.2, 12.6 and 13) spin ladder superconducting single crystals were grown using a modified mirror floating zone furnace with oxygen pressure up to 35 bar. The qualities of the as-grown single crystals were confirmed by polarized optical microscopy, neutron diffraction and X-ray diffraction methods. The sample compositions and homogeneity were measured using micro-X-ray fluorescence spectroscopy. The lattice parameters of each sample have been refined using the Rietveld method. The oxygen stoichiometry measurements which were performed by hydrogen reduction/thermogravimetry method show that all the three samples are slightly oxygen deficient even though high oxygen pressure was applied during growth. The high oxygen pressure is indispensible for growing highly Ca-doped Sr 14 À x Ca x Cu 24 O 41 single crystals. The susceptibility was measured along c-axis for all three compositions, fitting well with the one dimensional dimer model, consistent with the reported values of undoped Sr 14 Cu 24 O 41 parent compounds.