Ba₃Fe_1.56Ir_1.44O₉: A Polar Semiconducting Triple Perovskite with Near Room Temperature Magnetic Ordering

Abstract

The crystal chemistry and magnetic properties for two triple perovskites, BaFeIrO and BaNiIrO, grown as large, highly faceted single crystals from a molten strontium carbonate flux, are reported. Unlike the idealized AMM'O hexagonal symmetry characteristic of most triple perovskites, including BaNiIrO BaFeIrO possesses significant site-disorder, resulting in a noncentrosymmetric polar structure with trigonal symmetry. The valence of iron and iridium in the heavily distorted Fe/Ir sites was determined to be Fe(III) and Ir(V) by X-ray absorption near edge spectroscopy (XANES). Density functional theory calculations were conducted to understand the effect of the trigonal distortion on the local Fe(III)O electronic structure, and the spin state of iron was determined to be S = 5/2 by Mössbauer spectroscopy. Conductivity measurements indicate thermally activated semiconducting behavior in the trigonal perovskite. Magnetic properties were measured and near room temperature magnetic ordering (T = 270 K) was observed for BaFeIrO.

High-Pressure Synthesis and Ferrimagnetism of Ni3TeO6-Type Mn2ScMO6 (M = Nb, Ta)

“…In these dimer-units, each pair of cations is displaced away from the centers of octahedra along the c -axis in opposite directions as shown in Figure . This behavior is commonly observed in corundum-related structures and hexagonal perovskite structures containing M 2 O 9 dimer-units ,,− ,− and is attributed to electrostatic repulsions between the two closely spaced cations within the face-sharing octahedra of the dimer-unit. Correspondingly, these cation displacements result in three longer and three shorter metal oxygen bonds for each octahedra (see Table ).…”

Hexagonal Perovskites as Quantum Materials

“…The first of these is very highly structurally disordered, but in an interesting way. The complex disordered dimer material Ba3Fe1.56Ir1.44O9 116 adopts the hexagonal space group P3m1, with the lattice parameters a = 5.740 Å and c = 14.160 Å as shown in Figure 7. Interestingly, the site disorder between the Fe and Ir occurs within the dimers, where the dimerized sites are said to be unequally occupied by Fe and Ir, and in one of the triangular layers of octahedra but not the other.…”

Intrinsic Triple Order in A‐site Columnar‐Ordered Quadruple Perovskites: Proof of Concept

“…Thus, a systematic investigation of physical properties and magnetic structures of such novel A‐site ordered perovskites with different degree of charge doping is a promising avenue for future studies. It is known that cation ordering/disordering could have dramatic effects on properties of perovskite materials ,,…”