Crystal structures, strain analysis, and physical properties of Sr_{0.7}Ce_{0.3}MnO_{3}

Zhang, Zhaoming and Kennedy, Brendan J. and Howard, Christopher J. and Carpenter, Michael A. and Miiller, Wojciech and Knight, Kevin S. and Matsuda, Motohide and Miyake, Michihiro (2012) Crystal structures, strain analysis, and physical properties of Sr_{0.7}Ce_{0.3}MnO_{3}. Physical Review B, 85 (17). p. 174110. DOI

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We have studied the crystal structure of mixed-valence Sr0.7Ce0.3MnO3 from 4.2 to 973 K using high-resolution neutron powder diffraction. The crystal structure is tetragonal in space group I4/mcm at 4.2–923 K and cubic in Pm3̅ m at T ≥ 948 K. Lattice parameters and Mn-O bond distances, obtained by Rietveld refinement, have been used to derive the spontaneous strains and MnO6 octahedral distortion, which are interpreted in terms of strain/order parameter coupling using a single Landau free-energy expansion for a Pm3̅ m reference structure with two instabilities (R4+ and Γ3+). Two phase transitions were proposed: an octahedral tilting transition at Tc,φ ∼ 938 K (Pm3̅ m↔ I4/mcm, R4+), and an isosymmetric, electronically driven (Jahn-Teller–like) transition at Tc,JT ∼ 770 K (I4/mcm, R4+ ↔ I4/mcm, R4+ and Γ3+). The nature of the tilting transition appears to be tricritical, while that of the Jahn-Teller–like transition is second order. In addition to the contributions from octahedral tilting and Jahn-Teller–like distortions, there is an excess octahedral distortion at temperatures below 250 K; this is speculated to be associated with an anomaly observed over the temperature range of 275–300 K in the heat-capacity measurements.

Item Type: Article
Uncontrolled Keywords: 2012AREP; IA63;
Subjects: 03 - Mineral Sciences
Divisions: 03 - Mineral Sciences
Journal or Publication Title: Physical Review B
Volume: 85
Page Range: p. 174110
Identification Number:
Depositing User: Sarah Humbert
Date Deposited: 27 Jun 2012 14:56
Last Modified: 23 Jul 2013 10:04

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