Polar Ferromagnet Induced by Fluorine Positioning in Isomeric Layered Copper Halide Perovskites

• Published in: Inorganic chemistry Vol. 61; no. 7; pp. 3230 - 3239
• Main Authors: Han, Ceng, McNulty, Jason A, Bradford, Alasdair J, Slawin, Alexandra M. Z, Morrison, Finlay D, Lee, Stephen L, Lightfoot, Philip
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 21.02.2022
• ISSN: 0020-1669; 1520-510X
• DOI: 10.1021/acs.inorgchem.1c03726

We present the influence of positional isomerism on the crystal structure of fluorobenzyl­ammonium copper­(II) chloride perovskites A2CuCl4 by incorporating ortho-, meta-, and para-fluorine substitution in the benzylamine structure. Two-dimensional (2D) polar ferromagnet (3-FbaH)2CuCl4 (3-FbaH+ = 3-fluorobenzyl­ammonium) is successfully obtained, which crystallizes in a polar orthorhombic space group Pca21 at room temperature. In contrast, both (2-FbaH)2CuCl4 (2-FbaH+ = 2-fluorobenzyl­ammonium) and (4-FbaH)2CuCl4 (4-FbaH+ = 4-fluorobenzyl­ammonium) crystallize in centrosymmetric space groups P21/c and Pnma at room temperature, respectively, displaying significant differences in crystal structures. These differences indicate that the position of the fluorine atom is a driver for the polar behavior in (3-FbaH)2CuCl4. Preliminary magnetic measurements confirm that these three perovskites possess dominant ferromagnetic interactions within the inorganic [CuCl4]∞ layers. Therefore, (3-FbaH)2CuCl4 is a polar ferromagnet, with potential as a type I multiferroic. This work is expected to promote further development of high-performance 2D copper­(II) halide perovskite multiferroic materials.