Influence of Magnetic Anisotropy on the Ground State of [CH3NH3]Fe(HCOO)3: Insights into the Improper Modulated Magnetic Structure

Cañadillas-Delgado, Laura; Mazzuca, Lidia; Ling, Sanliang; Cliffe, Matthew J.; Fabelo, Oscar

Abstract

T h e h y b r i d p e r o v s k i t e s [ C H 3 N H 3 ] -CoxNix−1(HCOO)3 with x = 0, 0.25, 0.5, 0.75, and 1.0 possess multiple phase transitions, including incommensurate structures. Notably, [CH3NH3]Ni(HCOO)3 features a proper magnetically incommensurate structure ground state. To explore similar behavior, we investigated the isomorphous [CH3NH3]Fe-(HCOO)3 (1). A combination of magnetometry measurements, single crystal and powder neutron diffraction, and density functional theory calculations have been used to accurately determine and understand the sequence of nuclear and magnetic phases present in compound 1. At room temperature, it crystallizes in the Pnma space group with a perovskite structure. Below 170 K,
new satellite reflections indicate a transition to a modulated structure, refined in the Pnma(00γ)0s0 with q1 = 0.1662(2)c*. At 75 K, the satellite reflections become closer to the main reflections, indicating a second transition, which maintains the superspace group symmetry but decreases the modulation wave vector to q2 =0.1425(2)c*, i.e., with a longer modulation period. This modulation persists to 2 K, overlapping with the onset of 3D antiferromagnetic order at 17 K, offering a unique opportunity to study magneto-structural coupling. Our results point to an
improper magnetic modulated structure where, interestingly, the spins are perpendicular to those of previously reported compounds.

Citation

Cañadillas-Delgado, L., Mazzuca, L., Ling, S., Cliffe, M. J., & Fabelo, O. (2025). Influence of Magnetic Anisotropy on the Ground State of [CH3NH3]Fe(HCOO)3: Insights into the Improper Modulated Magnetic Structure. Inorganic Chemistry, 64(15), 7348–7363. https://doi.org/10.1021/acs.inorgchem.4c05404

• Journal Article Type: Article
• Acceptance Date: Mar 27, 2025
• Online Publication Date: Apr 9, 2025
• Publication Date: Apr 21, 2025
• Deposit Date: May 31, 2025
• Publicly Available Date: Jun 2, 2025
• Journal: Inorganic Chemistry
• Print ISSN: 0020-1669
• Electronic ISSN: 1520-510X
• Publisher: American Chemical Society
• Peer Reviewed: Peer Reviewed
• Volume: 64
• Issue: 15
• Pages: 7348–7363
• DOI: https://doi.org/10.1021/acs.inorgchem.4c05404
• Public URL: https://nottingham-repository.worktribe.com/output/47668904
• Publisher URL: https://pubs.acs.org/doi/10.1021/acs.inorgchem.4c05404