Nanocomposites and nanomaterials

Structural properties of iron-formate under high pressure
Wei Ziyu1, Liedienov N.A.1,2, Yu Hanlin1, Gaspar A.B.3, Real J.A.3, Levchenko G.G.1,2
1 State Key Laboratory of Superhard Materials, International Centre of Future Science, Jilin University. Qianjin Street, 2699, Changchun-130012, China.
E-mail: nikita.ledenev.ssp@gmail.com
2 Donetsk Institute for Physics and Engineering named after O. O. Galkin, NAS of Ukraine. Prospect Nauki, 46, Kyiv-03028, Ukraine.
3 Institut de Ciència Molecular/Departament de Química Inorgànica, Universitat de València. Catedràtric Beltrán 2, E-46980 Paterna València, Spain.

Hybrid organic-inorganic perovskites (HOIPs) have attracted a lot of recent research attention due to the diverse range of their physical and chemical properties including photovoltaic, optoelectronic, dielectric, ferroelectric, magnetic, ferroelastic, and multiferroic properties [1]. Among HOIP materials, the hybrid formate [(CH3)2NH2]M(HCOO)3 (M = Mn, Fe, Co, Ni) perovskites can exhibit both magnetic order and ferroelectricity at low temperature, as well as a possibility of magnetoelectric coupling in these compounds, which expands the prospect of their technical application [2].
It is well known that the functional properties of HOIPs change significantly with temperature. As another important thermodynamic parameter, pressure can also significantly vary the properties of these materials, especially the structural characteristics. Here, we performed in situ high-pressure X-ray diffraction and Raman spectroscopy studies of the [(CH3)2NH2]Fe(HCOO)3 formate using the diamond anvil cell (DAC) technique up to 10 GPa. The experimental results show that at about 6 GPa, the sample undergoes obvious structural transformation, and the characteristic peak positions of Raman spectra also shift significantly. The pronounced changes for the modes corresponding to the dimethylammonium cation and formate ion may indicate an order-disorder phase transition and the distortion of the metal-formate framework under high pressure, respectively.

1.	Li W., Stroppa A., Wang Z.-M., Gao S. Hybrid organic-inorganic perovskites // John Wiley & Sons, 2020. P. 292.
2.	Li W., Wang Z., Deschler F., Gao S., Friend R. H., Cheetham A. K. Chemically diverse and multifunctional hybrid organic-inorganic perovskites // Nature Reviews Materials-2017.-2.-P. 1-18.