Disorder effects in the S=1 antiferromagnetic spin ladder CaV2O4

We study the physical properties of the antiferromagnetic spin ladder CaV2O4 (CVO) and the Y-doped related compound Ca0.9Y0.1V2O4. In the latter. X-ray diffraction demonstrates the segregation of a small amount of a vanadium-perovskite impurity phase, leading to the formation of V vacancies within the main CVO-type structure. The 1D character of this calcium-vanadite enhances the influence of the vacancies on the electric and magnetic properties of Ca0.9Y0.1V2O4. Electrical transport is characterized by a variable-range hopping mechanism determined by the charging energy of nm-sized segments of V chains delimited by V vacancies, i.e. a Coulomb gap is formed at the Fermi level. These vacancies also locally affect the magnetic correlations, breaking the long-range AFM order observed in CaV2O4 and producing exchange bias when the Y-doped sample is cooled with an applied magnetic held. (C) 2015 Elsevier B.V. All rights reserved.