High-Pressure Synthesis and Ferrimagnetism of Ni₃TeO₆-Type Mn₂ScMO₆ (M = Nb, Ta)

Abstract

The corundum-related oxides Mn2ScNbO6 and Mn2ScTaO6 were synthesized at high pressure and high temperature (6 GPa and 1475 K). Analysis of the synchrotron powder X-ray diffraction shows that Mn2ScNbO6 and Mn2ScTaO6 crystallize in Ni3TeO6-type noncentrosymmetric crystal structures with space group R3. The asymmetric crystal structure was confirmed by second harmonic generation measurement. X-ray absorption near-edge spectroscopies indicate formal valence states of Mn2+ 2Sc3+Nb5+O6 and Mn2+ 2Sc3+Ta5+O6, also supported by the calculated bond valence sums. Both samples are electrically insulating. Magnetic measurements indicate that Mn2ScNbO6 and Mn2ScTaO6 order ferrimagnetically at 53 and 50 K, respectively, and Mn2ScTaO6 is found to have a field-induced magnetic transition.

Cocrystalline Polymer Films Exhibiting Second-Order Nonlinear Optical Properties

“…Space group assignment using X-ray diffraction in some cases results in ambiguous crystal structure classification due to the limitations of crystal structure refinement methods. Therefore, additional characterization methods, such as SHG, are necessary to distinguish between centrosymmetric and noncentrosymmetric space groups. − To the best of our knowledge, this is the first report of a hybrid host–guest cocrystalline polymer material with oriented domains without the need for electric field poling or molecularly engineered chromophores or polymers. More importantly, the work presented here highlights the use of semicrystalline polymers as a component in the synthesis of SHG-active cocrystalline materials, which is counter to current methods that use polymers as a noninteracting matrix in organic NLO materials.…”

A Polar Magnetic and Insulating Double Corundum Oxide: Mn2MnSbO6 with Ordered Mn(II) and Mn(III) Ions

“…The room-temperature SPXD pattern of Mn 2 MnSbO 6 can be well indexed with a hexagonal cell of a = 5.26 Å and c = 14.26 Å. Comparable unit cells have been reported for similar double corundum oxides Mn 2 FeMO 6 (M = Nb, Ta), Mn 2 ScMO 6 (M = Nb, Ta, Sb), , Mn 2 MWO 6 (M = Fe, Mn), , and Mn 2 FeSbO 6 . Space groups R 3 c , R 3, and R -3 c are reported for these oxides.…”

“…Mn 2+ 2 FeWO 6 spectrum is shifted well down in energy from the perovskite-Mn 2+ standard, as is typical of Ni 3 TeO 6 structure compounds. 13,18 The Mn 2 MnSbO 6 spectrum manifests a prominent/similar local peak feature in the same energy range, strongly suggesting a Mn 2+ 2 component in the compound formula. However, the absolute peak of the Mn 2 MnSbO 6 spectrum occurs at an energy characteristic of a Mn 3+ peak feature (i.e., compared to LaMn 3+ O 3 in the figure).…”

“…The calculated polarization is about 3.5 μC cm −2 , which is comparable with the value of 4.0 μC cm −2 calculated for a similar double corundum oxide Mn 2 ScTaO 6 . 18 Mn-K XANES. XANES measurements of the K-edges of 3d row transition metals in compounds have proven to be a useful probe of the transition metal valence/configuration.…”

“… − So far, the number of reported double corundum oxides is limited, presumably because most of them require high synthesis pressure (5 GPa or higher) to stabilize the structure type with relatively small A site ions, such as Mn 2+ and Ni 2+ . Most of the reported double corundum oxides have Mn 2+ ions in the A sites, for instance, Mn 2 BB ’O 6 ( B = Mn, Fe, Sc, or In; B ′ = W, Sb, Nb, Ta, or Mo). ,− For Mn 3 WO 6 and Mn 3 TeO 6 , the B sites are also occupied by Mn 2+ ions. However, to the best of our knowledge, there is no reported double corundum oxide containing Mn 3+ ions.…”