Magnetism of theFe2+andCe3+sublattices inCe2<

Abstract

The discovery of superconductivity in the 122 iron selenide materials above 30 K necessitates an understanding of the underlying magnetic interactions. We present a combined experimental and theoretical investigation of magnetic and semiconducting Ce2O2FeSe2 composed of chains of edgelinked iron selenide tetrahedra. The combined neutron diffraction and inelastic scattering study and density functional calculations confirm the ferromagnetic nature of nearest-neighbour Fe -Se -Fe interactions in the ZrCuSiAs-related iron oxyselenide Ce2O2FeSe2. Inelastic measurements provide an estimate of the strength of nearest-neighbor Fe -Fe and Fe -Ce interactions. These are consistent with density functional theory calculations, which reveal that correlations in the Fe-Se sheets of Ce2O2FeSe2 are weak. The Fe on-site repulsion UF e is comparable to that reported for oxyarsenides and K1−xFe2−ySe2, which are parents to iron-based superconductors.

Infinitely Adaptive Transition Metal Oxychalcogenides: The Modulated Structures of Ce2O2MnSe2 and (Ce0.78La0.22)2O2MnSe2

“…This suggests that two magnetic ordering processes occur (ordering of Mn 2+ and ordering of Ce ). Similar behaviour has been observed in related systems 25,48 . Pawley refinement was used to confirm that all magnetic peaks could be indexed with the nuclear unit cell.…”

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

“…1(d)] [14,15], while for the more electronegative M = Co 2+ analogue, 180°J 2 interactions * e.e.mccabe@kent.ac.uk dominate, leading to a magnetic structure with k vector k = ( 1 / 2 1 / 2 0) with in-plane moments and nn moments perpendicular to one another [18,19,21,22]. For M = Fe, Fe-Se-Fe J 2 interactions are ferromagnetic (FM) [10] (consistent with the FM chains of edge-linked FeSe 4 tetrahedra in Ce 2 O 2 FeSe 2 ) [23,24]. La 2 O 2 Fe 2 OSe 2 adopts a two-k-vector magnetic structure [k = ( 1 / 2 0 1 / 2 ) and k = (0 1 / 2 1 / 2 )] with in-plane moments directed along the Fe-O bonds, with FM J 2 and AFM J 2 interactions consistent with theory and nearest-neighbor moments orthogonal to one another [ Fig.…”

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+ .…”

“…All three structures can be adopted by Ce 2 O 2 FeSe 2 by modifying the synthesis conditions [4,13]. McCabe et al reported the nuclear and magnetic structure of bulk layered α-Ce 2 O 2 FeSe 2 [4,6]; the space group of the nuclear structure is Imcb (72). Nitsche et al observed all three polymorphs (which they label as oI -, oA-and mC-Ce 2 O 2 FeSe 2 according to their symmetry) in single crystals grown at different temperatures [13].…”

“…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].…”