Li4OBr2, an n = 1 member of the inverse Ruddlesden–Popper (iRP) phase Li3n+1O n Br n+1, was prepared for the first time by high-pressure (HP) synthesis. The changes in the stability and the ionic ...conductivity induced by F or I substitution for Br were also investigated by density functional theory (DFT) calculations and were experimentally attempted as well. The experimentally observed activation energy of Li4OBr2 was 0.63 eV, which was further lowered by F or I substitution for Br or the introduction of Li–Br defects.
The pyrochlore-type Ca
Bi
O
and Sr
Bi
O
have been synthesized from a low-temperature hydrothermal route using NaBiO
·nH
O as a starting material. The crystal structures of these compounds were ...refined using synchrotron powder X-ray diffraction data. The cell parameters were found to be a = 10.75021 (5) Å and 10.94132 (6) Å for Ca
Bi
O
and Sr
Bi
O
, respectively. Density functional theory calculations showed the metallic band structure, but the negligible mixing of O2 2p bands with the A-site alkaline-earth-metal states and weak overlap with the conduction bands result in the semiconducting behavior.
► The magnetoelectric effect has tremendous potential applications. ► Transition metal oxides provide a fertile playground for magnetoelectric phenomena. ► First-principles methods to study ...magnetoelectric phenomena are reviewed.
The search for materials displaying a large magnetoelectric effect has occupied researchers for many decades. The rewards could include not only advanced electronics technologies, but also fundamental insights concerning the dielectric and magnetic properties of condensed matter. In this article, we focus on the magnetoelectric effect in transition metal oxides and review the manner in which first-principles calculations have helped guide the search for (and increasingly, predicted) new materials and shed light on the microscopic mechanisms responsible for magnetoelectric phenomena.
Motivated by recent experimental results, we study the effect of size reduction on half-doped manganite, La(0.5)Ca(0.5)MnO(3), using the combination of density-functional theory (DFT) and dynamical ...mean-field theory (DMFT). We find that upon size reduction the charge-ordered antiferromagnetic phase, observed in bulk, is destabilized, giving rise to the stability of a ferromagnetic metallic state. Our theoretical results, carried out on a defect-free nanocluster in isolation, establish the structural changes that follow upon size reduction to be responsible for this. Our study further points out the effect of size reduction to be distinctively different from application of hydrostatic pressure. Interestingly, our DFT+DMFT study additionally reports the correlation-driven stability of the charge-orbitally ordered state in bulk La(0.5) Ca(0.5) MnO(3), even in the absence of long-range magnetic order.
Antisymmetric Dzyaloshinskii-Moriya (DM) interactions generating from the spin-orbit coupling induce various fascinating properties, like magnetoelectric (ME) effect, weak ferromagnetism and ...non-trivial topological spin textures like skyrmions, in real materials. Compared to their symmetric isotropic exchange counterpart, these interactions are generally of a weaker order of strength, creating modest twisting in the spin structure which results in weak ferromagntism or weak linear ME effect. Our proposed two-sublattice model, in contrast, predicts a hitherto unobserved, charge ordered non-collinear ferrimagnetic behavior with a considerably high magnetization \(\textbf{M}\) coexisting with a ferroelectric (FE) order with an electric polarization \(\textbf{P}\) and a strong cross coupling between them which is primarily driven by the inter-sublattice DM interactions. The key to realize these effects is the coupling between these microscopic interactions and the FE primary order parameter. We predict microscopic mechanisms to achieve electric field \(\textbf{E}\) induced spin-reorientation transitions and 180\(^{\circ}\) switching of the direction of \(\textbf{M}\). This model was realized in the hexagonal phase of LuFeO\(_3\) doped with electrons. This system shows \(P \sim\) 15 \(\mu\)C/cm\(^2\), \(M \sim\) 1.3 \(\mu_B\)/Fe and magnetic transition near room temperature (\(\sim\) 290 K). Our theoretical results are expected to stimulate further quest for energy-efficient routes to control magnetism for spintronics applications.
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