Lattice dynamics and spin excitations in the metal-organic framework [CH3NH3][Co(HCOO)3]

Lei Ding*, Claire V. Colin, Virginie Simonet, Chris Stock, Jean Blaise Brubach, Marine Verseils, Pascale Roy, Victoria Garcia Sakai, Michael M. Koza, Andrea Piovano, Alexandre Ivanov, Jose A. Rodriguez-Rivera, Sophie De Brion, Manila Songvilay

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract / Description of output

In metal-organic-framework (MOF) perovskites, both magnetic and ferroelectric orderings can be readily realized by compounding spin and charge degrees of freedom. The hydrogen bonds that bridge the magnetic framework and organic molecules have long been thought of as a key in generating multiferroic properties. However, the underlying physical mechanisms remain unclear. Here, we combine neutron diffraction, quasielastic and inelastic neutron scattering, and THz spectroscopy techniques to thoroughly investigate the dynamical properties of the multiferroic MOF candidate [CH3NH3][Co(HCOO)3] through its multiple phase transitions. The wide range of energy resolutions reachable by these techniques enables us to scrutinize the coupling between the molecules and the framework throughout the phase transitions and interrogate a possible magnetoelectric coupling. Our results also reveal a structural change around 220 K, which may be associated with the activation of a nodding donkey mode of the methylammonium molecule due to the ordering of the CH3 groups. Upon the occurrence of the modulated phase transition around 130 K, the methylammonium molecule undergoes a freezing of its reorientational motions, which is concomitant with a change of the lattice parameters and anomalies of collective lattice vibrations. No significant change has been however observed in the lattice dynamics around the magnetic ordering, which therefore indicates the absence of a substantial magnetoelectric coupling in zero field.

Original languageEnglish
Article number084405
Pages (from-to)1-11
Number of pages11
JournalPhysical Review Materials
Issue number8
Publication statusPublished - 18 Aug 2023

Keywords / Materials (for Non-textual outputs)

  • Rotational-dynamics
  • Transitions
  • Perovskites
  • Coexistence
  • Behaviour


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