Ca2MnO4 structural path: Following the negative thermal expansion at the local scale

Pedro Rocha-Rodrigues, Samuel S. M. Santos, Gonçalo N. P. Oliveira, Tiago Leal, Ivan P. Miranda, António M. dos Santos, João G. Correia, Lucy V. C. Assali, Helena M. Petrilli, João P. Araújo, and Armandina M. L. Lopes
Phys. Rev. B 102, 104115 – Published 28 September 2020
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Abstract

The oxygen octahedral rotations in Ca2MnO4, the first member of the CaO(CaMnO3)n Ruddlesden-Popper family, is probed through a set of complementary techniques, including temperature-dependent neutron and x-ray diffraction, combined with local probe studies and ab initio calculations. Here we demonstrate the enhancement of the uniaxial negative thermal expansion coefficient from 1.26±0.25 to 21±1.8 ppm/K at the second order I41/acd to I4/mmm structural phase transition, providing direct evidence for the corkscrew atomic mechanism. We establish, also, that the predicted I4/mmm high symmetry is attained around 1050 K. At lower temperatures, within the 10–1000 K temperature range, our first-principles calculations and detailed analysis of the Ca local environment reveals that the reported Aba2 structural phase, coexisting with the I41/acd one, cannot describe correctly this compound. On the other hand, our data allow for the coexistence of the locally identical I41/acd and Acam structural phases.

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  • Received 12 May 2020
  • Revised 29 July 2020
  • Accepted 28 August 2020

DOI:https://doi.org/10.1103/PhysRevB.102.104115

©2020 American Physical Society

Physics Subject Headings (PhySH)

Nuclear PhysicsCondensed Matter, Materials & Applied Physics

Authors & Affiliations

Pedro Rocha-Rodrigues1, Samuel S. M. Santos1, Gonçalo N. P. Oliveira1, Tiago Leal1, Ivan P. Miranda2, António M. dos Santos3, João G. Correia4, Lucy V. C. Assali2, Helena M. Petrilli2, João P. Araújo1, and Armandina M. L. Lopes1,*

  • 1IFIMUP, Institute of Physics for Advanced Materials, Nanotechnology and Photonics, Departamento de Física e Astronomia da Faculdade de Ciências da Universidade do Porto, Rua do Campo Alegre, 687, 4169-007 Porto, Portugal
  • 2Universidade de São Paulo, Instituto de Física, Rua do Matao, 1371, 05508-090 São Paulo, São Paulo, Brazil
  • 3Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
  • 4C2TN, Centro de Ciências e Tecnologias Nucleares, Departamento de Engenharia e Ciências Nucleares, Instituto Superior Técnico, Universidade de Lisboa, Estrada Nacional 10, 2695-066 Bobadela LRS, Portugal

  • *armandina.lopes@fc.up.pt

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Vol. 102, Iss. 10 — 1 September 2020

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