Floating Zone Single Crystal Growth of γ‑CoV₂O₆ with Substantially Enhanced Crystal Size and Quality

Here, we report the growth of centimeter-sized γ-CoV₂O₆ single crystals by the optical floating zone method which are suitable for neutron scattering experiments. Our floating zone grown single crystals have higher magnetic ordering temperatures of 7.8 K, much more clearly visible magnetization plateaus, and substantially enhanced saturation magnetizations compared to flux-grown single crystals, which is also important with regard to the presence of orbital moment contributions within these <i>S</i> = 3/2 systems. Our centimeter-sized single crystals grown by the optical floating zone technique open the way toward the measurement of the peculiar magnetic properties of this intriguing system by means of elastic and inelastic neutron scattering and have been characterized by X-ray and neutron diffraction measurements

Canted Antiferromagnetism on Rectangular Layers of Fe²⁺ in Polymorphic CaFeSeO

From stoichiometric amounts of CaO, Fe, and Se, pure powders and single crystals of quaternary Ca[FeSe2/2O2/2]∞2 can be obtained by solid-state reaction and self-flux growth, respectively. The as-synthesized compound exhibits a polymorphic crystal structure, where the two modifications have different stacking sequences of [FeSe2/2O2/2]2−∞2 layers. The two polymorphs have similar unit cells but different crystal symmetries (<i>Cmc</i>2₁ and <i>Pnma</i>), of which the former is non-centrosymmetric. Fe is divalent (d⁶) and high-spin, as proven by X-ray spectroscopy, Mössbauer spectroscopy, and powder neutron diffraction data. The latter two, in combination with magnetic susceptibility and specific heat data, reveal a long-range antiferromagnetic spin order (<i>T</i>_N = 160 K) with a minor spin canting. CaFeSeO is an electronic insulator, as confirmed by resistivity measurements and density functional theory calculations. The latter also suggest a relatively small energy difference between the two polymorphs, explaining their intimate intergrowth