Magnetic structure of frustrated Haldane chain compound CaV$_{2}$O$_{4}$

While the Haldane chain, (Heisenberg spin-1 chain with nearest neighbor antiferromagnet interactions) has been much studied and shown to have gapped magnon excitations. The effect of frustrated and single ion-anisotropy has not been investigated experimentally. Theory suggests that frustration can enhance the multi-particle spectrum and the combination of frustration and anisotropy can drive the system into a gapless chiral phase. CaV$_{2}$O$_{4}$ is a candidate for such a system. This compound consists of two inequivalent one-dimensional chains consisting of spin-1 V$^{3+}$ ions which have antiferromagnetic first and second neighour interactions. Interchain coupling gives rise to long-range order below $T_{N}$= 71K. Neutron diffraction measurements will be described. They reveal collinear spin order within the chains and canting between chains, with the average spin direction along the \textbf{b} axis. The ordered spin moment was also measured and found to be 1 $\mu _{B}$ per Vanadium; this reduction of 50{\%} from full spin ordering suggests loss of moment due to quantum fluctuations. Finally, preliminary inelastic neutron scattering reveals a gap due to single-ion anisotropy. In addition a steep dispersion along the \textbf{c} (chain) direction and much weaker dispersions along \textbf{a} and \textbf{b} confirm the one-dimensional nature of CaV$_{2}$O$_{4}$.