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