In this study, scientists from Warwick, UCL, Oxford, the National High Magnetic Field Laboratory and Eastern Washington University describe a novel form of symmetry breaking driven by chemical intervention: an anisotropic change in magnetic properties is induced by ionic substitution of an isotropic species. The chemical system in question is a three-dimensional hybrid organic-inorganic framework with different molecular bridges linking spin-1 Ni(II) ions along the axial and equatorial directions. The study makes use of a raft of complementary techniques that includes x-ray diffraction, magnetometry, susceptometry, x-ray fluorescence and ESR, backed up by data modelling and percolation calculations. We find that replacing 80% of the anisotropic Ni(II) with isotropic Zn(II) ions induces a 22% enhancement in single-ion anisotropy. This substantial change is accomplished by an anisotropic lattice expansion and exploits the relative donor atom hardness as a structural design tool. In this way it is possible to tune the single-ion anisotropy of a magnetic lattice site by Zn-substitution on nearby sites, suggesting that the combination of anisotropic organic frameworks and metal ions of different radii may be exploited to tune the single-ion properties of magnetically isolated spins to desired values. This will be useful in the control of magnetization reversal and slow relaxation in self-assembled arrays of single-ion magnets composed of d− or f−elements for use in spin-based electronic devices. J. L. Manson et al. J. Am. Chem. Soc. 143, 4633 (2021)

• Publication: https://pubs.acs.org/doi/10.1021/jacs.0c12516
• DOI: https://pubs.acs.org/doi/10.1021/jacs.0c12516