High-Pressure Synthesis and Ferrimagnetic Ordering of the B-Site-Ordered Cubic Perovskite Pb₂FeOsO₆

Abstract

PbFeOsO was prepared for the first time by using high-pressure and high-temperature synthesis techniques. This compound crystallizes into a B-site-ordered double-perovskite structure with cubic symmetry Fm3̅m, where the Fe and Os atoms are orderly distributed with a rock-salt-type manner. Structure refinement shows an Fe-Os antisite occupancy of about 16.6%. Structural analysis and X-ray absorption spectroscopy both demonstrate the charge combination to be PbFeOsO. A long-range ferrimagnetic transition is found to occur at about 280 K due to antiferromagnetic interactions between the adjacent Fe and Os spins with a straight (180°) Fe-O-Os bond angle, as confirmed by X-ray magnetic circular-dichroism measurements. First-principles theoretical calculations reveal the semiconducting behavior as well as the Fe(↑)Os(↓) antiferromagnetic coupling originating from the superexchange interactions between the half-filled 3d orbitals of Fe and t orbitals of Os.

Structural and Magnetic Transitions in CaCo3V4O12 Perovskite at Extreme Conditions

“…Tuning the properties of perovskite materials by doping or chemical substitution as well as creating completely new perovskites can greatly extend the applicability and functionality of these systems and indicate novel directions for their possible applications. For these reasons, the new unusual perovskites are intensively fabricated and investigated. − Generally, conventional perovskites (ABO 3 ) are composed of two types of cations, namely, an octahedrally coordinated cation B and a cation A with a variable coordination number. More sophisticated double perovskites, e.g., those that are called “A-site ordered” with the general formula AA′ 3 B 4 O 12 comprise one more site (A′) for cations with an unusual two-dimensional square oxygen coordination (Figure ).…”

Site-Specified Two-Dimensional Heterojunction of Pt Nanoparticles/Metal–Organic Frameworks for Enhanced Hydrogen Evolution

“…Additionally, X-ray absorption near-edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) measurements were employed to study the local structures of Ni and Pt species. It is well-known that XANES at a 3d element K edge and a 5d element L 3 edge is highly sensitive to the electronic structure. − From the Pt L 3 -edge XANES spectrum in Figure e, the energy position and spectral features of Pt/MOF-O are similar to those of Pt foil, indicating that Pt in Pt/MOF-O is mainly in the metal state. However, the average valence state of Pt in Pt/MOF-O is higher than that in Pt/MOF-C (inset of Figure e).…”

A’–B Intersite Cooperation-Enhanced Water Splitting in Quadruple Perovskite Oxide CaCu3Ir4O12

“…The ECSA of each sample was obtained by determining the double-layer capacitance at non-Faradaic potential range, according to the method reported by McCrory et al 36 A series of cyclic voltammetry (CV) measurements were performed at various scan rates (20,40,60,80, 100, and 120 mV•s −1 ) in the potential window between 1.031 and 1.13 V vs RHE. Then, a linear plot was estimated by plotting Δj = (j + − j − )/2 at (i a − i c ) at 1.08 V vs RHE and the scan rate.…”

“…In the double perovskite La 2 CuIrO 6 , Cu 2+ and Ir 4+ are arranged in a rock-salt type cation ordering, where the Cu−O−Ir bond angles are larger than 140°and can approach 180°. In this case, electron hopping between, for example, orbitals at two lattice sites has a higher energy barrier because of the larger crystal field splitting energy on 5d electrons,60,61 and hopping between t 2g and, for example, orbitals is prohibited by the orbital symmetry.62,63 However, in CaCu 3 Ir 4 O 12 , the small bond angle (110.7°) is closer to that of the 90°model. Electron hopping between Cu 2+ and Ir 4+ via oxygen is allowed on both the orbital symmetry and energy levels.…”