Abstract
PbMO3 (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 PbFeO3 remain unclear. Herein, we reveal that PbFeO3 crystallizes into an unusual 2ap × 6ap × 2ap orthorhombic perovskite super unit cell with space group Cmcm. The distinctive crystal construction and valence distribution of Pb2+0.5Pb4+0.5FeO3 lead to a long range charge ordering of the -A-B-B- type of the layers with two different oxidation states of Pb (Pb2+ and Pb4+) 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 Fe3+ magnetic sublattices with competing anisotropic energies, giving rise to the spin reorientation at such a high critical temperature.
Highlights
PbMO3 (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
Except for a tiny Fe2O3 impurity phase, all the diffraction peaks can be indexed based on an unusual 2ap × 6ap × 2ap orthorhombic perovskite super unit cell, where ap refers to the pseudolattice parameter of a cubic ABO3 perovskite subcell
In summary, the crystal structure and physical properties of PbFeO3 were investigated in detail through synchrotron X-ray diffraction (SXRD), electron diffraction (ED), X-ray absorption spectroscopy (XAS), hard X-ray photoemission spectroscopy (HAXPES), neutron powder diffraction (NPD), and theoretical calculations
Summary
Our theoretical investigations reveal that the peculiar charge ordering of Pb generates two Fe3+ magnetic sublattices with competing anisotropic energies, giving rise to the spin reorientation at such a high critical temperature. The perovskite family of RFeO3 (R = rare earth) exhibits various spin-related properties such as multiferroicity[23,24,25], laser-induced ultrafast spin reorientation (SR)[26,27], and ultrafast photomagnetic recording[28], and it is anticipated that the evolution of magnetism and spin structure of PbFeO3 as a function of temperature, magnetic field or pressure will be rich. As the Fe spin reorientation is regarded to be closely related to anisotropic R–Fe magnetic exchange interactions, the current PbFeO3 with nonmagnetic A-site Pb ions may provide a new avenue for understanding the distinct underlying mechanism of SR transition. Related mechanisms are proposed to explain the SR of PbFeO3
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