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Updated: Jun 27, 2025
Synthesis of Single-Crystalline Core-Shell Metal-Organic Frameworks
Published on: February 10, 2023
J_{eff}=1/2 Hyperoctagon Lattice in Cobalt Oxalate Metal-Organic Framework
Hajime Ishikawa1, Shusaku Imajo1, Hikaru Takeda1
1Institute for Solid State Physics, University of Tokyo, Kashiwa, Chiba, 277-8581, Japan.
Abstract:
We report the magnetic properties of a cobalt oxalate metal-organic framework featuring the hyperoctagon lattice. Our thermodynamic measurements reveal the J_{eff}=1/2 state of the high-spin Co^{2+} (3d^{7}) ion and the two successive magnetic transitions at zero field with two-stage entropy release. ^{13}C-NMR measurements reveal the absence of an internal magnetic field in the intermediate temperature phase. Multiple field-induced phases are observed before full saturation at around 40 T. We argue the unique cobalt oxalate network gives rise to the Kitaev interaction and/or a bond frustration effect, providing an unconventional platform for frustrated magnetism on the hyperoctagon lattice.
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