Tripoliti, EK;
Dobson, DP;
Fortes, AD;
Thomson, AR;
Schofield, PF;
Wood, IG;
(2023)
Structure and thermal expansion of end-member olivines I: Crystal and magnetic structure, thermal expansion, and spontaneous magnetostriction of synthetic fayalite, Fe₂SiO₄, determined by high-resolution neutron powder diffraction.
Mineralogical Magazine
, 87
(6)
pp. 789-806.
10.1180/mgm.2023.66.
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Abstract
The lattice parameters and the crystal and magnetic structures of Fe2SiO4 have been determined from 10 K to 1453 K by high-resolution time-of-flight neutron powder diffraction. Fe2SiO4 undergoes two antiferromagnetic phase transformations on cooling from room temperature: the first, at 65.4 K, is to a collinear antiferromagnet with moments on two symmetry-independent Fe ions; the second transition, at ~23 K, is to a structure in which the moments on one of the sets of Fe ions (those on the ‘M1 site’) become canted. The magnetic unit cell is identical to the crystallographic (chemical) unit cell and the space group remains Pbnm throughout. The magnetic structures have been refined and the results found to be in good agreement with previous studies; however, we have determined the spontaneous magnetostrictive strains, which have not been reported previously. In the paramagnetic phase of Fe2SiO4, at temperatures of 70 K and above, we find that the temperature dependence of the linear thermal expansion coefficient of the b axis takes an unusual form. In contrast to the behaviour of the expansion coefficients of the unit-cell volume and of the a and c axes, which show the expected reduction in magnitude below ~300 K, that of the b axis remains almost constant between ~70 K and 1000 K.
| Type: | Article |
|---|---|
| Title: | Structure and thermal expansion of end-member olivines I: Crystal and magnetic structure, thermal expansion, and spontaneous magnetostriction of synthetic fayalite, Fe₂SiO₄, determined by high-resolution neutron powder diffraction |
| Open access status: | An open access version is available from UCL Discovery |
| DOI: | 10.1180/mgm.2023.66 |
| Publisher version: | https://doi.org/10.1180/mgm.2023.66 |
| Language: | English |
| Additional information: | Copyright © The Author(s), 2023. Published by Cambridge University Press on behalf of The Mineralogical Society of the United Kingdom and Ireland. This is an Open Access article, distributed under the terms of the Creative Commons Attribution licence (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted re-use, distribution and reproduction, provided the original article is properly cited. |
| Keywords: | fayalite, olivine, thermal expansion, magnetism, crystal structure |
| UCL classification: | UCL UCL > Provost and Vice Provost Offices > UCL BEAMS UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Earth Sciences |
| URI: | https://discovery-pp.ucl.ac.uk/id/eprint/10176366 |
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