Flux synthesis, crystal structures, and physical properties of new lanthanum vanadium oxyselenides

Abstract

The new lanthanum vanadium oxyselenides LaVSeO, LaVSeO, LaVSeO, LaVSeO, and LaVSeO were synthesized in eutectic NaI/KI fluxes, and their crystal structures were determined using single-crystal and powder X-ray diffraction experiments. LaVSeO and LaVSeO adopt known structure types, whereas LaVSeO, LaVSeO, and LaVSeO crystallize in hitherto unknown structure types. The main building blocks of these compounds are chains of edge-sharing VSe, VSeO, and/or VSeO octahedra, linked together by edge-sharing OLa and/or OLaV tetrahedra forming fluorite-like ribbons. LaVSeO, LaVSeO, and LaVSeO contain only V(iii) ions, whereby LaVSeO and LaVSeO contain mixtures of either V(iii)/V(iv) or V(iii)/V(v) cations. Magnetic measurements indicate Curie-Weiss paramagnetism and magnetic ordering of the vanadium moments at low temperatures. More precisely, we observe antiferromagnetism for LaVSeO, metamagnetism for LaVSeO, ferromagnetism for LaVSeO and a complex magnetic structure for LaVSeO.

Structural Diversity of Rare-Earth Oxychalcogenides

“…The connectivity of these OLn 4 units (and the possibility of including oxide ions in the coordination environment of the M x + cation giving OLn 3 M units) generates a huge diversity of structure types. This is perhaps best illustrated by the La–V–O–Se family of materials (Figure ) in which the OLn 4 units form 2D sheets of edge-connected tetrahedra as in La 2 O 2 S, 2D fragments (truncated by OLn 3 V tetrahedra) as in La 7 VO 7 Se 5 , and 1D ribbons of OLn 4 and OLn 3 V tetrahedra as in La 13 V 7 O 15 Se 16 .…”

“…La 4 O 4 MnSe 3 is closely related to the Gd 4 O 4 TiSe 4 structure but contains fewer Se 2– anions as Ti 4+ is replaced with Mn 2+ . For Gd 4 O 4 TiSe 4 , the Mn–Se layers are separated by bands of OLa 4 or OLa 3 Mn units (four units wide) . La 6 O 6 MnSe 4 is an extension of the La 4 O 4 MnSe 3 structure but with wider six-unit wide OLa 4 /OLa 3 Mn bands separating the Mn–Se layers .…”

“…For Gd 4 O 4 TiSe 4 , the Mn–Se layers are separated by bands of OLa 4 or OLa 3 Mn units (four units wide) . La 6 O 6 MnSe 4 is an extension of the La 4 O 4 MnSe 3 structure but with wider six-unit wide OLa 4 /OLa 3 Mn bands separating the Mn–Se layers . In β-La 2 O 2 MSe 2 (o P -La 2 O 2 MSe 2 ) (M = Mn, Fe) , two divalent cations (Fe 2+ or Mn 2+ ) replace Ti 4+ , forming a tetrahedral MSe 4 site in addition to the octahedral MSe 4 O 2 site in the M–Se layers.…”

“Soft” Alkali Bromide and Iodide Fluxes for Crystal Growth

“…The ABI fluxes have also been employed to synthesize a variety of oxychalcogenide compounds. These are predominately oxyselenides (Tougait and Ibers, 2000b , c , 2001 ; Nitsche et al, 2014 ; Liu et al, 2015 ; Peschke et al, 2015 , 2017a , b ; Peschke and Johrendt, 2016 , 2017 ), but also include oxysulfides (Zeng et al, 1999 , 2002 ; Huang et al, 2000 ; Chi et al, 2016 ), and oxytellurides (Liu et al, 2007 ). In many cases, the ABI flux is utilized as a recrystallizing agent.…”

Synthesis, Crystal Structure, and Physical Properties of Layered LnCrSe2O (Ln = Ce–Nd)

“…To date, researchers are interested in the oxychalcogenides based on late transition metals (Fe, Co, Cu, Ag, Zn, Cd) for their abundant physical properties and potential applications. Taking Fe as an example, the reported Fe-based oxychalcogenides include the superconducting [Li 0.8 ­Fe 0.2 OH]­[Fe Q ] ( Q = S, Se), − the semiconductive CaFe Q O ( Q = S, Se), − the antiferromagnetic Ln 2 Fe 2 Q 2 O 3 ( Ln = La, Ce; Q = S, Se), and Sr 2 Fe 3 ­Se 2 O 3 with much complex magnetic ordering. , Even though the oxychalcogenides in the Ln / M /Q/O ( Ln = rare earth metal, M = early transition metals) family have also been explored, researches on their physical properties remain far to be desired. − Hence, more work should focus on the early transition metal oxychalcogenides as well as their physical properties.…”