Ferroelasticity in a metal–organic framework perovskite; towards a new class of multiferroics

Li, Wei and Zhang, Zhiying and Bithell, Erica G. and Batsanov, Andrei S. and Barton, Phillip T. and Saines, Paul J. and Jain, Prashant and Howard, Christopher J. and Carpenter, Michael A. and Cheetham, Anthony K. (2013) Ferroelasticity in a metal–organic framework perovskite; towards a new class of multiferroics. Acta Materialia, 61 (13). pp. 4928-4938. ISSN 1359-6454 DOI 10.1016/j.actamat.2013.04.054

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Official URL: http://www.sciencedirect.com/science/article/pii/S...

Abstract

Abstract A metal–organic framework perovskite, [(CH2)3NH2][Mn(HCOO)3], exhibits a weakly first order ferroelastic phase transition at ∼272 K, from orthorhombic Pnma to monoclinic P21/n, and a further transition associated with antiferromagnetic ordering at ∼8.5 K. The main structural changes, through the phase transition, are orientational ordering of the azetidium groups and associated changes in hydrogen bonding. In marked contrast to conventional improper ferroelastic oxide perovskites, the driving mechanism is associated with the X-point of the cubic Brillouin zone rather than being driven by R- and M-point octahedral tilting. The total ferroelastic shear strain of up to ∼5% is substantially greater than found for typical oxide perovskites, and highlights the potential of the flexible framework to undergo large relaxations in response to local structural changes. Measurements of elastic and anelastic properties by resonant ultrasound spectroscopy show some of the characteristic features of ferroelastic materials. In particular, acoustic dissipation below the transition point can be understood in terms of mobility of twin walls under the influence of external stress with relaxation times on the order of ∼10−7 s. Elastic softening as the transition is approached from above is interpreted in terms of coupling between acoustic modes and dynamic local ordering of the azetidium groups. Subsequent stiffening with further temperature reduction is interpreted in terms of classical strain–order parameter coupling at an improper ferroelastic transition which is close to being tricritical. By way of contrast, there are no overt changes in elastic or anelastic properties near 9 K, implying that any coupling of the antiferromagnetic order parameter with strain is weak or negligible.

Item Type: Article
Uncontrolled Keywords: 2013AREP, IA66,
Subjects: 03 - Mineral Sciences
Divisions: 03 - Mineral Sciences
Journal or Publication Title: Acta Materialia
Volume: 61
Page Range: pp. 4928-4938
Identification Number: 10.1016/j.actamat.2013.04.054
Depositing User: Sarah Humbert
Date Deposited: 07 Jul 2013 02:28
Last Modified: 08 Aug 2013 12:14
URI: http://eprints.esc.cam.ac.uk/id/eprint/2826

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