Blog

Tobias Bird, Jessica Woodland-Scott, Lei Hu, Michael Wharmby, Jun Chen, Andrew Goodwin, Mark Senn, Phys. Rev. B 101(2020), 064306. We use a symmetry-motivated approach to analysing X-ray pair distribution functions to study the mechanism of negative thermal expansion in two ReO3-like compounds; ScF3 and CaZrF6. Both average and local structure suggest that it is the flexibilityRead more

Fernando Pomiro, Chris Ablitt, Nicholas C. Bristowe, Arash A. Mostofi, Coongjae Won, Sang-Wook Cheong, and Mark S. Senn. arXiv:2001.05189 Hybrid improper ferroelectrics (HIFs) have been intensely studied over the last few years to gain understanding of their ferroelectric switching pathways and rich domain structure. There is a fundamental need to understand how the octahedral tilts andRead more

Chris Ablitt, Harriet McCay, Sarah Craddock, Lauren Cooper, Emily Reynolds, Arash A. Mostofi, Nicholas C. Bristowe, Claire A. Murray, and Mark S. Senn. Chem. Mater. 2020, 32, 1, 605-610. By tuning the tolerance factor, t, of the Ruddlesden–Popper oxide Ca2MnO4 through isovalent substitutions, we show that the uniaxial coefficient of linear thermal expansion (CLTE) ofRead more

S. R. Popuri, R. Decourt, J. A. McNulty, M. Pollet, A. D. Fortes, F. D. Morrison, M. S. Senn, and J. W. G. Bos.  J. Phys. Chem. C  10.1021/acs.jpcc.8b10520 The phonon–glass electron crystal concept is one of the key guiding principles for the development of efficient thermoelectric materials. Here, we confirm that SrTiO3 becomes aRead more

Wei-Tin Chen, Chris Ablitt, Nicholas C. Bristowe, Arash A. Mostofi, Takashi Saito, Yuichi Shimakawaf and Mark S. Senn .  Chem. Commun., 2019, Advance Article  10.1039/C8CC09614G We report the high pressure synthesis of a layered perovskite Ca2GeO4 which is found to have the Ruddlesden–Popper structure with I41/acd symmetry. Consonant with our recent predictions [Ablitt et al.,Read more

Ablitt C, Mostofi AA, Bristowe NC and Senn MS (2018) Control of Uniaxial Negative Thermal Expansion in Layered Perovskites by Tuning Layer Thickness. Front. Chem. 6:455. doi: 10.3389/fchem.2018.00455 Uniaxial negative thermal expansion (NTE) is known to occur in low $n$ members of the An+1$BnO3n+1 Ruddlesden–Popper layered perovskite series with a frozen rotation of BO_6 octahedra about the layering axis. PreviousRead more

Mark S. Senn and Nicolas C. Bristowe, Acta Crystallographica Section A: Foundations and Advances, 2018, Volume A74, pages 308-321 A group-theoretical approach is used to enumerate the possible couplings between magnetism and ferroelectric polarization in the parent Pm-3m perovskite structure. It is shown that third-order magnetoelectric coupling terms must always involve magnetic ordering at theRead more

Hanna L. B. Boström,  Mark S. Senn and Andrew L. Goodwin, Nature Communications (2018) 9:2380 The central goal of crystal engineering is to develop precise control over material function via rational design of structure. A particularly successful realisation of this paradigm is the example of hybrid improper ferroelectricity in layered perovskite materials, where cation vacanciesRead more

Wei-Tin Chen, Chin-Wei Wang, Hung-Cheng Wu, Fang-Cheng Chou, Hung-Duen Yang, Arkadiy Simonov, and Mark S. Senn, Phys. Rev. B 97, 144102 (2018)   There has recently been renewed interest in improper ferroelectricity due to the discovery of a “hybrid” mechanism by which two nonpolar lattice modes couple to a third polar mode. Here, the authorsRead more

Chris Ablitt, Sarah Craddock, Mark S. Senn, Arash A. Mostofi & Nicholas C. Bristowe, npj Computational Materials 3, Article number: 44 (2017) doi:10.1038/s41524-017-0040-0   Why is it that ABO3 perovskites generally do not exhibit negative thermal expansion (NTE) over a wide temperature range, whereas layered perovskites of the same chemical family often do? It isRead more