On the Ferrimagnetic State of CrCl2(pyz)2
Abstract
Van der Waals layered ferromagnetic compounds with high two-dimensional electronic conductivity holds strong potential for quantum computing, future unconventional superconductors, catalysts, batteries, and fuel cells. We suggest a minimal theoretical model to understand the magnetic properties of the metal-organic framework CrCl2(pyz)2 (pyz=pyrazine). Using a Hubbard model we show that the groundstate is dominated by a specific configuration of delocalized electrons on the pyz sites with a ferrimagnetic coupling to the localized spins on the Cr sites. This model suggests a magnetic moment of 2μB which is remarkably close to the experimental value of 1.8 μB [K. S. Pedersen et al., Nat. Chem. 10, 1056-1061 (2018)]. From Weiss mean-field theory we predict a weak ferromagnetic Cr-Cr coupling of ≈ 0.9 meV. This is consolidated by second order perturbation theory of the RKKY interaction yielding a Cr-Cr coupling of ≈ 5 meV. Understanding the interactions in these types of compounds can facilitate designs of metal-organic compounds with tailored magnetic properties.
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