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

Abstract

The layered oxyselenides with the formula LnCrSe2O (Ln = Ce–Nd) were synthesized via molten salt methods. The isostructural compounds crystallize in the monoclinic space group of C2/m. The crystal structures feature ∞ 2[CrSe2O]3– motifs stacked along the a axis, which are separated by Ln 3+ ions. The ∞ 2[CrSe2O]3– layers are composed of [Cr1Se6]9– and [Cr2Se4O2]9– octahedra via corner and edge sharing. Powder X-ray diffraction results confirm the phase purities of the as-synthesized compounds. LnCrSe2O (Ln = Ce–Nd) show typical antiferromagnetic ordering with T N = 125, 120, and 118 K, respectively. Heat capacity measurement for NdCrSe2O indicates that the Debye temperature is 278.4 K. Similar metal-to-semiconductor phase transitions were observed for LnCrSe2O (Ln = Ce–Nd) plates with transition temperatures of 115, 109, and 95 K, respectively. NdCrSe2O also possesses a magnetoresistance effect at low temperature (<25 K) with a significant positive magnetoresistance ∼ 16% at 2 K and 1 T.

Structural Diversity of Rare-Earth Oxychalcogenides

“…LnCrOSe 2 (Ln = Pr, Nd; Q = S, Se) comprises corner-linked chains of edge-shared CrS 6 and edge-sharing CrO 2 S 4 octahedra separated by ribbons of two OLn 3 Cr tetrahedra. LnCrOQ 2 (Ln = Ce–Nd; Q = S, Se) are isostructural to LaVOSe 2 (Figure ).…”

Antiferromagnetic quaternary chalco-halide Ba3(FeS4)I with long Fe⋯Fe distances

“…The distinct packing habits of different anions always construct remarkable ''structural-functional units'' (SFUs), and the interplay of these SFUs imbues the materials with unexpected physical properties. [7][8][9][10][11][12] For instance, the quasi-2D antiferromagnetic Ln 2 Fe 2 Q 2 O 3 (Ln = Ce, Pr, Nd, Sm; Q = S, Se) [13][14][15][16][17][18] contains alternately stacked [Ln 2 O 2 ] 2+ and [Fe 2 OS 2 ] 2À SFUs, while the (Li 0.8 Fe 0.2 )OHFeQ (Q = S, Se) [19][20][21] superconductors feature [(Li 0.8 Fe 0.2 )OH] and [FeQ] SFUs. Moreover, many other Fe-based oxychalcogenides have also been explored, including CaFeQO (Q = S, Se), [22][23][24][25][26] Ca 2 O 3 Fe 2.6 S 2 , 27 Sr 2 Fe 3 Se 2 O 3 , 28,29 A E2 Fe 2 Q 2 O (A E = Sr, Ba; Q = S, Se), [30][31][32] A E2 F 2 Fe 2 OQ 2 (A E = Sr, Ba; Q = S, Se), 33,34 Ln 2 O 2 FeSe 2 (Ln = La, Ce), [35][36][37][38] and so on.…”