title: Symmetry Switching of Negative Thermal Expansion by Chemical Control.
abstract: The layered perovskite Ca3-xSrxMn2O7 is shown to exhibit a switching from a material exhibiting uniaxial negative to positive thermal expansion as a function of x. The switching is shown to be related to two closely competing phases with different symmetries. The negative thermal expansion (NTE) effect is maximized when the solid solution is tuned closest to this region of phase space but is switched off suddenly on passing though the transition. Our results show for the first time that, by understanding the symmetry of the competing phases alone, one may achieve unprecedented chemical control of this unusual property.
authors.affiliation: Department of Chemistry, University of Oxford , Inorganic Chemistry Laboratory, South Parks Road, Oxford, OX1 3QR, U.K.
authors.forename: Mark S
authors.initials: MS
authors.lastname: Senn
authors.affiliation: Diamond Light Source, Harwell Campus, Oxfordshire, OX11 0DE, U.K.
authors.forename: Claire A
authors.initials: CA
authors.lastname: Murray
authors.affiliation: Laboratory for Pohang Emergent Materials and Max Plank POSTECH Center for Complex Phase Materials, Pohang University of Science and Technology , Pohang 790-784, Korea.
authors.forename: Xuan
authors.initials: X
authors.lastname: Luo
authors.affiliation: Laboratory for Pohang Emergent Materials and Max Plank POSTECH Center for Complex Phase Materials, Pohang University of Science and Technology , Pohang 790-784, Korea.
authors.forename: Lihai
authors.initials: L
authors.lastname: Wang
authors.affiliation: Rutgers Center for Emergent Materials and Department of Physics Astronomy, Rutgers University , Piscataway, New Jersey 08854, United States.
authors.forename: Fei-Ting
authors.initials: FT
authors.lastname: Huang
authors.affiliation: Laboratory for Pohang Emergent Materials and Max Plank POSTECH Center for Complex Phase Materials, Pohang University of Science and Technology , Pohang 790-784, Korea.|Rutgers Center for Emergent Materials and Department of Physics Astronomy, Rutgers University , Piscataway, New Jersey 08854, United States.
authors.forename: Sang-Wook
authors.initials: SW
authors.lastname: Cheong
authors.affiliation: Diamond Light Source, Harwell Campus, Oxfordshire, OX11 0DE, U.K.
authors.forename: Alessandro
authors.initials: A
authors.lastname: Bombardi
authors.affiliation: Department of Materials, and the Thomas Young Centre, Imperial College London , London SW7 2AZ, U.K.
authors.forename: Chris
authors.initials: C
authors.lastname: Ablitt
authors.affiliation: Department of Materials, and the Thomas Young Centre, Imperial College London , London SW7 2AZ, U.K.
authors.forename: Arash A
authors.initials: AA
authors.lastname: Mostofi
authors.affiliation: Department of Materials, and the Thomas Young Centre, Imperial College London , London SW7 2AZ, U.K.
authors.forename: Nicholas C
authors.initials: NC
authors.lastname: Bristowe