Observation of novel charge ordering and spin reorientation in perovskite oxide PbFeO.

PbMO (M = 3d transition metals) family shows systematic variations in charge distribution and intriguing physical properties due to its delicate energy balance between Pb 6s and transition metal 3d orbitals. However, the detailed structure and physical properties of PbFeO remain unclear. Herein, we reveal that PbFeO crystallizes into an unusual 2a × 6a × 2a orthorhombic perovskite super unit cell with space group Cmcm. The distinctive crystal construction and valence distribution of PbPbFeO lead to a long range charge ordering of the -A-B-B- type of the layers with two different oxidation states of Pb (Pb and Pb) in them. A weak ferromagnetic transition with canted antiferromagnetic spins along the a-axis is found to occur at 600 K. In addition, decreasing the temperature causes a spin reorientation transition towards a collinear antiferromagnetic structure with spin moments along the b-axis near 418 K. Our theoretical investigations reveal that the peculiar charge ordering of Pb generates two Fe magnetic sublattices with competing anisotropic energies, giving rise to the spin reorientation at such a high critical temperature.