Magnetic transition in α-NaCuPO4 with Cu-O chains

The magnetic properties and specific heat have been studied on α-NaCuPO4, an analog of ion-battery material LiFePO4. A ferromagnetic-like transition at 23 K was observed for the first time by the isofield magnetization measurement and confirmed by isothermal magnetization below 23 K. The compound obeys Curie-Weiss law with an antiferromagentic coupling feature. A canted antiferromagentism was suggested to account for the ferromagnetic-like transition. The contribution from the orbital magnetic moment is found to be non-ignorable. Furthermore, specific heat shows that the magnetic transition is broadened and the critical temperature is enhanced under magnetic field, revealing a low dimensionality feature.