Abstract
The compound contains cations with spin and has an orthorhombic structure at room temperature containing zigzag chains of V atoms running along the axis. We have grown single crystals of and report crystallography, static magnetization, magnetic susceptibility , ac magnetic susceptibility, heat capacity , and thermal expansion measurements in the temperature range of 1.8–350 K on the single crystals and on polycrystalline samples. An orthorhombic-to-monoclinic structural distortion and a long-range antiferromagnetic (AF) transition were found at sample-dependent temperatures and , respectively. In two annealed single crystals, another transition was found at . In one of the crystals, this transition is mostly due to impurity phase that grows coherently in the crystals during annealing. However, in the other crystal the origin of this transition at 200 K is unknown. The shows a broad maximum at associated with short-range AF ordering and the anisotropy of above is small. The anisotropic data below show that the (average) easy axis of the AF magnetic structure is the axis. The data indicate strong short-range AF ordering above , consistent with the data. We fitted our data by a Heisenberg chain model, where is the (next)-nearest-neighbor exchange interaction. We find and surprisingly, (or ). The interaction between these chains leading to long-range AF ordering at is estimated to be .
17 More- Received 23 December 2008
DOI:https://doi.org/10.1103/PhysRevB.79.104432
©2009 American Physical Society