二維（2D）凡德瓦化合物CuCrP2S6有低操作電壓、高開關比、高耐用性和高熱穩定性等優點，適合做開關、記憶體、仿生突觸和太陽能發電等應用。我們以化學氣相傳輸法製備CuCrP2S6單晶，並進行了31P的核磁共振（NMR）研究。
為了探討各向異性效應，我們在外加磁場平行於c軸和平行於ab平面的情況下，測量單晶樣品隨溫度變化的奈特位移。以31P原子核為探測點，透過與Cr3+自旋的交互作用確定了各向異性的超精細耦合。此外，31P NMR譜線揭示了鐵電相變溫度TC1 ≃ 190 K和TC2 ≃ 145 K附近的異常變化。這些觀察結果為Cu+離子的偏好占位提供了證據，而這解釋了CuCrP2S6的多鐵性相變。

We report a 31P nuclear magnetic resonance (NMR) study of van der Waals compound of CuCrP2S6. To explore the anisotropic effects, we have carried out the temperature-dependent Knight shift measurement on the single crystalline specimen with the external field perpendicular and parallel to the c axis. By using the phosphorus nuclear spin as a local probe, we have determined the anisotropic hyperfine coupling through the interactions with the Cr3+ spins. In addition, our temperature-dependent 31P NMR spectra have revealed anomalous features near ferroelectric transition temperatures TC1 ≃ 190 K and TC2 ≃ 145 K. The observations provide evidence for the preferential occupancy of Cu+ cations which is responsible for the multi-ferroelectric transitions in CuCrP2S6.

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