Ruddlesden-Popper Oxyfluorides LaNiCuOF (0 ≤ ≤ 1): Impact of the Ni/Cu Ratio on the Thermal Stability and Magnetic Properties.

Ruddlesden-Popper oxyfluorides of the substitution series LaNiCuOF (0 ≤ ≤ 1) were obtained by topochemical fluorination with polyvinylidene fluoride (PVDF) of oxide precursors LaNiCuO. The thermal stability and the temperature-dependent unit cell evolution of the oxyfluorides were investigated by high-temperature XRD measurements. The oxyfluoride with = 0.6 shows the highest decomposition temperature of ∼ 520 °C, which is significantly higher than the ones found for the end members LaNiOF ( = 0) ∼ 460 °C and LaCuOF ( = 1) ∼ 430 °C. The magnetic properties of all LaNiCuOF oxyfluorides were characterized by field- and temperature-dependent measurements as well as DFT calculations of the magnetic ground state. An antiferromagnetic ordering was derived for all substitution levels. For the Néel temperature (), a nonlinear dependence on the copper content was found, and comparably high values of in the region of 200-250 K were observed in the broad composition range of 0.3 ≤ ≤ 0.8.