Magnetism and ESR of the Seff=12 antiferromagnet BaCo2(SeO3)3·3H2O with dimer-chain structure

We report the magnetism and ESR of the ${S}_{\text{eff}}=1/2$ compound ${\mathrm{BaCo}}₂{({\mathrm{SeO}}₃)}₃\ifmmode\cdot\else\textperiodcentered\fi{}3{\mathrm{H}}₂\mathrm{O}$ with dimer-chain structure. The magnetic susceptibility and heat capacity show that the compound is antiferromagnetically ordered at ${T}_{\text{N}}=7.6$ K. The magnetization $M(H)$ curve at 2 K presents a spin-flop transition within 2.6--3.0 T when the magnetic field is applied along the $ab$ plane ($H\ensuremath{\perp}c$), pointing to the easy axis-like anisotropy. In high magnetic field, the magnetization increases nearly linearly until saturation at about 22 T, indicating a classical-like behavior. The magnetization process can be described with the intradimer exchange ${J}₁=\ensuremath{-}20.0$ K and interdimer exchanges ${J}₂=\ensuremath{-}14.6$ K and ${J}₃=\ensuremath{-}6.2$ K. Thus, ${\mathrm{BaCo}}₂{({\mathrm{SeO}}₃)}₃\ifmmode\cdot\else\textperiodcentered\fi{}3{\mathrm{H}}₂\mathrm{O}$ is approximately a three-dimensional antiferromagnet, although structurally it contains dimer chains.