Transition metal iodates. IV. Crystallographic,magnetic and nonlinear optic survey of the copper iodates

Three anhydrous polymorphs of cupric iodate, two hydrates, and the basic iodate salesite have been investigated. α-Cu(IO₃)₂ is monoclinic, space group P2₁, with a = 5.551 ± 0.008, b = 5.101 ± 0.004, c = 9.226 ± 0.010 Å and β = 95°4′ ± 11′, with two formulas in the unit cell. Below Θ_N = 8.5 K, α-Cu(IO₃)₂ is antiferromagnetic and also pyroelectric. β-Cu(IO₃)₂ is triclinic, space group $\text{P}\text{1}$, with a = 11.230 ± 0.006, b = 11.368 ± 0.009, c = 10.630 ± 0.009 Å, α = 99°18.3′ ± 0.3′, β = 107°0.4′ ± 0.2′ and γ = 114°23.8′ ± 0.2′ and eight formulas per unit cell: the crystal is paramagnetic to 1.4K. γ-Cu(IO₃)₂ is monoclinic, space group $\text{P2}{}_1\text{m}$, with a = 4.977 ± 0.004, b = 6.350 ± 0.004, c = 8.160 ± 0.004 Å and β = 92°20′ ± 4′, with two formulas per unit cell; γ-Cu(IO₃)₂ becomes antiferromagnetic below Θ_N = 5 K. Cu(IO₃)₂·2H₂O is monoclinic, space group $\text{P2}{}_1\text{c}$, with a = 6.725 ± 0.005, b = 4.770 ± 0.007, c = 11.131 ± 0.013 Å and β = 103°1′ ± 4′, with two formulas per unit cell; Cu(IO₃)₂·2H₂O is paramagnetic to 1.4 K. $\text{Cu(IO}{}_3\text{)}{}_2\text{·}\text{2}\text{3}\text{H}{}_2\text{O}$ (mineral bellingerite) is triclinic, space group $\text{P}\text{1}$, with a = 7.197 ± 0.005, b = 7.824 ± 0.004, c = 7.904 ± 0.004 Å, α = 105°2′ ± 2′, β = 97°7′ ± 2′ and γ = 92°54′ ± 2′ with three formulas per unit cell; this crystal is paramagnetic to 1.4 K, with a moderate antiferromagnetic Cu-Cu interaction. Cu(OH)IO₃ (mineral salesite) is orthorhombic, with a = 10.772 ± 0.004, b = 6.702 ± 0.002 and c = 4.769 ± 0.002 Å and four formulas per unit cell. The magnetic susceptibility indicates the possibility of antiferromagnetic ordering at 162 K; strong antiferromagnetic interactions give Θ_p = ?340 K. The only copper iodate studied that generates second harmonics is α-Cu(IO₃)₂. Indexed powder patterns are given for all six compounds.