Abstract
Metal-organic magnets (MOMs), modular magnetic materials where metal atoms are connected by organic linkers, are promising candidates for next-generation quantum technologies. MOMs readily form low-dimensional structures and so are ideal systems to realize physical examples of key quantum models, including the Haldane phase, where a topological excitation gap occurs in integer-spin antiferromagnetic (AFM) chains. Thus, far the Haldane phase has only been identified for S = 1, with S ≥ 2 still unrealized because the larger spin imposes more stringent requirements on the magnetic interactions. Here, we report the structure and magnetic properties of CrCl2(pym) (pym = pyrimidine), a new quasi-1D S = 2 AFM MOM. We show, using X-ray and neutron diffraction, bulk property measurements, density-functional theory calculations, and inelastic neutron spectroscopy (INS), that CrCl2(pym) consists of AFM CrCl2 spin chains (J1 = −1.13(4) meV) which are weakly ferromagnetically coupled through bridging pym (J2 = 0.10(2) meV), with easy-axis anisotropy (D = −0.15(3) meV). We find that, although small compared to J1, these additional interactions are sufficient to prevent observation of the Haldane phase in this material. Nevertheless, the proximity to the Haldane phase together with the modularity of MOMs suggests that layered Cr(II) MOMs are a promising family to search for the elusive S = 2 Haldane phase.
| Original language | English |
|---|---|
| Pages (from-to) | 1783-1792 |
| Number of pages | 10 |
| Journal | Journal of the American Chemical Society |
| Volume | 145 |
| Issue number | 3 |
| DOIs | |
| State | Published - Jan 25 2023 |
| Externally published | Yes |
Funding
J.P. and M.J.C. acknowledge the School of Chemistry, University of Nottingham, for support from the Hobday bequest. A.J.M. acknowledges funding from EPSRC (EP/P003532/1). The authors acknowledge networking support via the EPSRC Collaborative Computational Projects, CCP9 (EP/M022595/1) and CCP-NC (EP/T026642/1). Computing resources were provided by the Sulis HPC service (EP/T022108/1). We acknowledge the ILL for beamtime under proposal EASY-778. We acknowledge ISIS for beamtime under proposal RB2090119. J.P. acknowledges Jesum Alves Fernandes for training and assistance with XPS analysis. J.P. acknowledges Benjamin Weare for TEM analysis. Heat capacity measurements were performed using the Advanced Materials Characterisation Suite, funded by EPSRC Strategic Equipment Grant EP/M000524/1. J.P. and M.J.C. acknowledge Sia\u0302n Dutton and Joseph Paddison for useful discussions.