Structural and magnetic characterization of iron oxyselenidesCe2O2Fe2OSe2and

Abstract

We present here an investigation of the magnetic ordering in the Mott insulating oxyselenide materials Ln 2 O 2 Fe 2 OSe 2 (Ln = Ce, Nd). Neutron powder diffraction data are consistent with a noncollinear multi-k ordering on the iron sublattice structure and analysis indicates a reduced magnetic correlation length perpendicular to the [Fe 2 O] 2+ layers. The magnetic role of the Ln 3+ cations is investigated and Ce 3+ moments are found to order at T 16 K.

Crystal field excitations and magnons: Their roles in oxyselenides Pr2O2M2OSe2(

“…Magnetic Bragg reflections are observed on cooling below ∼90 K in zero field. These reflections, consistent with the 2k magnetic structure reported for Ln 2 O 2 Fe 2 OSe 2 (Ln = La, Nd, Ce) [17,37] and Sr 2 F 2 Fe 2 OS 2 [11], increase smoothly on cooling (Supplemental Material [51]). As for other materials, magnetic reflections are anisotropically broadened, suggesting stacking faults in the magnetic structure perpendicular to the Fe 2 O layers.…”

“…Sequential Rietveld refinements in zero field showed that the unit cell parameters decreased on cooling, similar to behavior reported for other Ln 2 O 2 Fe 2 OSe 2 analogues, with a more rapid decrease in the c parameter below T N , presumably due to magnetostrictive effects [17,37]. However, a slight increase in the c parameter was observed below ∼22.5 K (see Fig.…”

“…In the layered copper oxide superconducting systems, the electronic state of Pr 3+ ions (leading to magnetic or nonmagnetic ground states) was key to whether copper-based superconductivity evolved on cooling [28][29][30]. This has prompted significant research into possible coupling between the lanthanide and transition metal sublattices in layered systems [24,[31][32][33][34][35][36][37][38][39][40][41][42][43][44][45]. Probing the crystalline electric field (CEFs) of the lanthanide ions by INS experiments has given insights into both the lanthanide magnetism and the transition metal sublattice [41,46].…”

Crystal structure and magnetic modulation in β−Ce2O2FeSe2

“…Ce-Fe oxyselenides, where ordered Ce moments are required to fit the diffraction data and persist to surprisingly high temperatures [4,6,7,11]. An excellent fit to the PND data is achieved using this type of model, and the refined profiles for 2+ .…”

“…One important family of compounds is those with general composition Ln 2 O 2 MSe 2 (Ln = La, Ce; M = Mn, Fe, Zn, Cd) [3][4][5][6][7][8][9][10][11] and closely related composition such as La 2 O 2 Cu 2−4x Cd 2x Se 2 [12]. These materials are semiconductors with band gaps varying from ∼0.3 to ∼3.3 eV [1,[3][4][5]8,10,11,[13][14][15][16].…”