Synthesis and Magnetic Properties of the KCu(IO) Compound with [CuO] Chains.

The new quaternary iodate KCu(IO) has been prepared by hydrothermal synthesis. KCu(IO) crystallizes in the monoclinic space group 2/ with unit cell parameters = 9.8143(4) Å, = 8.2265(4) Å, = 10.8584(5) Å, β = 91.077(2)°, and = 4. The crystals are light blue and translucent. There are three main building units making up the crystal structure: [KO] irregular polyhedra, [CuO] distorted octahedra, and [IO] trigonal pyramids. The Jahn-Teller elongated [CuO] octahedra connect to each other via corner sharing to form [CuO] zigzag chains along [010]; the other building blocks separate these chains. The Raman modes can be divided into four groups; the lower two groups into mainly lattice modes involving K and Cu displacements and the upper two groups into mainly bending and stretching modes of [IOE], where E represents a lone pair of electron. At low temperatures, the magnetic susceptibility is characterized by a broad maximum centered at ∼5.4 K, characteristic for antiferromagnetic short-range ordering. Long-range magnetic ordering at = 1.32 K is clearly evidenced by a sharp anomaly in the heat capacity. The magnetic susceptibility can be very well described by a spin = 1/2 antiferromagnetic Heisenberg chain with a nearest-neighbor spin exchange of ∼8.9 K.