Structural and magnetic properties of RTiNO2 (R=Ce, Pr, Nd) perovskite nitride oxides

• The oxide nitride perovskites RTiNO2 (R=Ce, Pr) have been prepared and their structures determined.
• Diffraction measurements indicate short range cis-order of O and N, but no long range order.
• Compounds are paramagnetic with Weiss constants that vary from −28 to −42 K.
• CeTiO2N and NdTiO2N deviate from Curie–Weiss behavior below 150 and 30 K, respectively.

Neutron powder diffraction indicates that CeTiNO2 and PrTiNO2 crystallize with orthorhombic Pnma symmetry (Ce: a=5.5580(5), b=7.8369(7), and c=5.5830(4) Å; Pr: a=5.5468(5), b=7.8142(5), and c=5.5514(5) Å) as a result of a–b+a– tilting of the titanium-centered octahedra. Careful examination of the NPD data, confirms the absence of long range anion order in both compounds, while apparent superstructure reflections seen in electron diffraction patterns provide evidence for short range anion order. Inverse magnetic susceptibility plots reveal that the RTiNO2 (R=Ce, Pr, Nd) compounds are paramagnetic with Weiss constants that vary from −28 to −42 K. Effective magnetic moments for RTiNO2 (R=Ce, Pr, Nd) are 2.43 μB, 3.63 μB, and 3.47 μB, respectively, in line with values expected for free rare-earth ions. Deviations from Curie–Weiss behavior that occur below 150 K for CeTiNO2 and below 30 K for NdTiNO2 are driven by magnetic anisotropy, spin–orbit coupling, and crystal field effects.

The structure and magnetism of the oxide nitride perovskites RTiNO2 (R=Ce, Pr, Nd) have been explored. The average symmetry is shown to be Pnma with a random distribution of oxide and nitride ions and a−b+a− tilting of the titanium-centered octahedra, but electron diffraction shows evidence for short range anion order. All three compounds are paramagnetic but deviations from the Curie Weiss law are seen below 150 K for R=Ce and below 30 K for R=Nd. Figure optionsDownload as PowerPoint slide