Cobalt ordering in layered Bi2Sr2CoO6+δ single crystal

[[abstract]]Insulating Bi2Sr2CoO6+δ is nearly isomorphic with the Bi(2201)-type high-Tc superconductors. Magnetic and calorimetric studies were carried out on single crystal samples of this layered compound. Based on magnetic measurements, the cobalt ions undergo a canted antiferromagnetic ordering at TN=159 K. A low-temperature neutron diffraction study of the magnetic-structure is in progress. The molar magnetic susceptibility χab(H⊥c) above 200 K can be well fitted by the Curie-Weiss form χab(T)=χ0+C/(T-&thetas;p), with χ0=0.56 cm3/mol, Curie constant C=3.2×10-2 cm3 K/mol and Curie-Weiss intercept &thetas;p=159 K. There is no magnetic specific heat peak, however, prevailing around TN. this anomalous calorimetric behavior is attributed to the two-dimensional quantum spin fluctuation of Co spins above TN in the layered compound as previously observed for Cu spins in (Gd1.85Ce0.15)CuO4-δ and La2CuO4-δ[[fileno]]2010102010157[[department]]物理