Antiferromagnetic spin-1 large-D phase in organic spin-chain crystals

Low-dimensional magnetism, including the Haldane phase and large single ion anisotropy (large-D) phase, has received ongoing attention due to their potential applications in quantum computing and molecular spintronics. However, the lack of materials possessing S = 1 one-dimensional spin-chain with antiferromagnetic intrachain interaction (J) and single ion anisotropy (D) has hindered the investigation and practical implementation of this topic. In this study, iron(ii) phthalocyanine (FePc) crystals in & beta;-phase (& beta;-FePc) hosting molecular chains along the b axis are prepared as revealed by X-ray diffraction (XRD). The molecular orientation is found to be almost upright within the naturally cleaved bc plane as determined by synchrotron-based near-edge X-ray absorption fine structure spectroscopy (NEXAFS). & beta;-FePc crystals exhibit clear magnetic anisotropy with the easy plane perpendicular to the b axis, antiferromagnetic intrachain exchange interaction and a large D value. These results demonstrate experimentally that the & beta;-FePc crystal is a new antiferromagnetic spin-1 large-D phase material. This discovery expands the frontiers of low-dimensional magnetism research in organic molecular crystals, providing a new platform to study the topological quantum phase transition in one-dimensional spin chains.