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

Wang, Chun-Hai, Ainsworth, Chris, Gui, Don-Yun, McCabe, E.E., Tucker, Matthew G., Evans, Ivana, Evans, J. S. O. (2015) Infinitely Adaptive Transition Metal Oxychalcogenides: The Modulated Structures of Ce2O2MnSe2 and (Ce0.78La0.22)2O2MnSe2. Chemistry of Materials, 27 (8). pp. 3121-3134. ISSN 0897-4756. (doi:10.1021/acs.chemmater.5b00666) (The full text of this publication is not currently available from this repository. You may be able to access a copy if URLs are provided)

The full text of this publication is not currently available from this repository. You may be able to access a copy if URLs are provided. (Contact us about this Publication)
Official URL
http://dx.doi.org/10.1021/acs.chemmater.5b00666

Abstract

This article reports the syntheses, structures, and physical properties of the oxychalcogenides (Ce1–xLax)2O2MnSe2 with x = 0–0.7. These materials have a layered structure related to that of the LaOFeAs-derived superconductors but with the transition metal sites 50% occupied. Ce2O2MnSe2 contains alternating layers of composition: [Ce2O2]2+ and [MnSe2]2–. The size mismatch between the layers leads to an incommensurate structure with a modulation vector of q = ?a*+ 0b*+0.5c* with ? = 0.158(1), which can be described with a (3 + 1)D superspace structural model in superspace group Cmme(?,0,1/2)0s0 [67.12]. There is a strong modulation of Mn site occupancies, leading to a mixture of corner- and edge-sharing MnSe4/2 tetrahedra in the [MnSe2]2– layers. The modulation vector can be controlled by partial substitution of Ce3+ for larger La3+, and a simple commensurate case was obtained for (Ce0.78La0.22)2O2MnSe2 with ? = 1/6. The materials respond to the change in relative size of the oxide and chalcogenide blocks by varying the ratio of corner- to edge-sharing tetrahedra. The superspace model lets us unify the structural description of the five different ordering patterns reported to date for different Ln2O2MSe2 (Ln = lanthanide) materials. Mn moments in Ce2O2MnSe2 and (Ce0.78La0.22)2O2MnSe2 order antiferromagnetically below TN = 150 K, and Ce moments order below ?70 K. The magnetic structures of both materials have been determined using neutron diffraction. Both materials are semiconductors; Ce2O2MnSe2 has ? = 9 × 10–6 ?–1 cm–1 at room temperature and an activation energy for charge carrier mobility from RT to 170 °C of ?0.4 eV.

Item Type: Article
DOI/Identification number: 10.1021/acs.chemmater.5b00666
Subjects: Q Science > QD Chemistry > QD478 Solid State Chemistry
Q Science > QD Chemistry
Q Science > QD Chemistry > QD156 Inorganic synthesis
Q Science > QD Chemistry > QD473 Physical properties in relation to structure
Divisions: Faculties > Sciences > School of Physical Sciences
Faculties > Sciences > School of Physical Sciences > Functional Materials Group
Depositing User: Emma McCabe
Date Deposited: 13 Dec 2016 17:06 UTC
Last Modified: 29 May 2019 18:29 UTC
Resource URI: https://kar.kent.ac.uk/id/eprint/59675 (The current URI for this page, for reference purposes)
  • Depositors only (login required):