Infinitely Adaptive Transition Metal Oxychalcogenides: The Modulated Structures of Ce₂O₂MnSe₂ and (Ce_0.78La_0.22)₂O₂MnSe₂

Abstract

. (2015) 'Innitely adaptive transition metal oxychalcogenides : the modulated structures of Ce2O2MnSe2 and (Ce0.78La0.22)2O2MnSe2.', Chemistry of materials., 27 (8). pp. 3121-3134. Further information on publisher's website:http://dx.doi.org/10.1021/acs.chemmater.5b00666 Publisher's copyright statement: This document is the Accepted Manuscript version of a Published Work that appeared in nal form in Chemistry of Materials, copyright c 2015 American Chemical Society after peer review and technical editing by the publisher. To access the nal edited and published work see http://dx.doi.org/10.1021/acs.chemmater.5b00666. Additional information:Use policyThe full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. 2-. The size mismatch between the layers leads to an incommensurate structure with a modulation vector of q = αa*+ 0b*+0.5c* with α = 0.158(1), which can be described with a (3+1)D superspace structural model in superspace group Cmme(α0 cm -1 at room temperature and an activation energy for charge carrier mobility from RT to 170 °C of ~0.4 eV. INTRODUCTIONInorganic materials built from the stacking of well-defined sublayers form a large, diverse and technologically important family. Exploitable behaviour exhibited by such layered systems includes high-temperature superconductivity,

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+ .…”

“…ISODIS-TORT [18] (http://stokes.byu.edu/iso/isotropy.php) was used to derive the low temperature magnetic structure. We note that the (correct) magnetic form factor of Ce 3+ appears to be consistently mislabeled as "Ce 2+ " in International Tables for Crys-tallography (Volume C) [19] and consequently in the scattering factor databases of TA and other diffraction software [11]. Selected figures of structures were drawn using Vesta [20].…”

“…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]. For example, layered La 2 O 2 CdSe 2 was reported as a wide-gap (3.3 eV) semiconductor and investigated as an optoelectronic device component [14,15].…”

“…Three basic structure types have been observed for Ln 2 O 2 MSe 2 compositions to date. Most adopt a layered structure (α phase) which can be modulated in either a commensurate or incommensurate manner within individual layers to accommodate different transition metal arrangements [8,10,11]. There are also two nonlayered structures reported (orthorhombic β phase and monoclinic Pb 2 HgCl 2 O 2 -type γ phase) [3,13].…”

Flux Synthesis, Crystal Structures, and Magnetism of the Series La2n+2MnSen+2O2n+2 (n = 0–2)

“…Numerous new compounds with the general formula RE 2 TSe 2 O 2 (RE = La, Ce; T = Cd, Fe, Mn, Zn) [1][2][3][4][5][6][7][8][9] have been discovered and their structures and magnetism have been studied. Among the particular families, different polymorphs may exist which makes the diversity even bigger.…”