Abstract Oxide heterostructures exhibit a vast variety of unique physical properties. Examples are unconventional superconductivity in layered nickelates and topological polar order in (PbTiO 3 ) n .../(SrTiO 3 ) n superlattices. Although it is clear that variations in oxygen content are crucial for the electronic correlation phenomena in oxides, it remains a major challenge to quantify their impact. Here, we measure the chemical composition in multiferroic (LuFeO 3 ) 9 /(LuFe 2 O 4 ) 1 superlattices, mapping correlations between the distribution of oxygen vacancies and the electric and magnetic properties. Using atom probe tomography, we observe oxygen vacancies arranging in a layered three-dimensional structure with a local density on the order of 10 14 cm −2 , congruent with the formula-unit-thick ferrimagnetic LuFe 2 O 4 layers. The vacancy order is promoted by the locally reduced formation energy and plays a key role in stabilizing the ferroelectric domains and ferrimagnetism in the LuFeO 3 and LuFe 2 O 4 layers, respectively. The results demonstrate pronounced interactions between oxygen vacancies and the multiferroic order in this system and establish an approach for quantifying the oxygen defects with atomic-scale precision in 3D, giving new opportunities for deterministic defect-enabled property control in oxide heterostructures.
The natural mineral azurite Cu(3)(CO(3))(2)(OH)(2) is a frustrated magnet displaying unusual and controversially discussed magnetic behavior. Motivated by the lack of a unified description for this ...system, we perform a theoretical study based on density functional theory as well as state-of-the-art numerical many-body calculations. We propose an effective generalized spin-1/2 diamond chain model which provides a consistent description of experiments: low-temperature magnetization, inelastic neutron scattering, nuclear magnetic resonance measurements, magnetic susceptibility as well as new specific heat measurements. With this study we demonstrate that the balanced combination of first principles with powerful many-body methods successfully describes the behavior of this frustrated material.
Bi and Pb ions with charge degree of freedom depending on 6s 2 and 6s 0 electronic configurations were combined with the Mn ion in a perovskite oxide. Comprehensive theoretical and experimental ...investigations revealed the Bi3+ 0.5Pb2+ 0.5Mn3+ 0.5Mn4+ 0.5O3 charge ordered state with CE-type spin and dz 2 orbital orderings as observed in La0.5Ca0.5MnO3, Nd0.5Sr0.5MnO3, and Bi0.5Sr0.5MnO3. The charge and orbital orderings were preserved above 500 K owing to the stereochemical activity of Bi3+ and Pb2+ ions which stabilized the structural distortion.
Abstract
High-mobility two-dimensional carriers originating from surface Fermi arcs in magnetic Weyl semimetals are highly desired for accessing exotic quantum transport phenomena and for topological ...electronics applications. Here, we demonstrate high-mobility two-dimensional carriers that show quantum oscillations in magnetic Weyl semimetal SrRuO
3
epitaxial films by systematic angle-dependent, high-magnetic field magnetotransport experiments. The exceptionally high-quality SrRuO
3
films were grown by state-of-the-art oxide thin film growth technologies driven by machine-learning algorithm. The quantum oscillations for the 10-nm SrRuO
3
film show a high quantum mobility of 3.5 × 10
3
cm
2
/Vs, a light cyclotron mass, and two-dimensional angular dependence, which possibly come from the surface Fermi arcs. The linear thickness dependence of the phase shift of the quantum oscillations provides evidence for the non-trivial nature of the quantum oscillations mediated by the surface Fermi arcs. In addition, at low temperatures and under magnetic fields of up to 52 T, the quantum limit of SrRuO
3
manifests the chiral anomaly of the Weyl nodes. Emergence of the hitherto hidden two-dimensional Weyl states in a ferromagnetic oxide paves the way to explore quantum transport phenomena for topological oxide electronics.
Here, we propose an idea to realize noncollinear ferrimagnetic orders with a considerably high magnetization M and their coupling with an improper ferroelectric (FE) order in hexagonal LuFeO_{3} type ...systems which exhibit interesting topological orders. These magnetic and magnetoelectric phenomena are driven by the antisymmetric Dzyaloshinskii-Moriya interactions between the magnetic ions and their coupling with the ferroelectricity. The proposed two-sublattice magnetic system, generated by a specific charge-ordered state, forms multiple energetically close, noncollinear ferrimagnetic orders. This offers a platform to manipulate the microscopic magnetic interactions and to trigger spin-reorientation (SR) transitions by various efficient means. The two-sublattice structure was realized in the hexagonal phase of LuFeO_{3} doped with electrons. The proposed electron-doped systems are expected to exhibit switchable electric polarization (P∼6–15 μC/cm^{2}), considerably high magnetization (M∼1.1–1.3μ_{B}/Fe), and magnetic transition near room temperature (∼275–290K). Based on the coupling between the magnetic interactions and the FE primary order parameter observed in this system, microscopic mechanisms to achieve electric field E induced SR transitions and 180^{∘} switching of the direction of M are discussed.
Despite several reports on the surface phase transformations from a layered to a disordered spinel and a rock-salt structure at the surface of the Ni-rich cathodes, the precise structures and ...compositions of these surface phases are unknown. The phenomenon, in itself, is complex and involves the participation of several contributing factors. Of these factors, transition metal (TM) ion migration toward the interior of the particle and hence formation of TM-densified surface layers, triggered by oxygen loss, is thermodynamically probable. Here, we simulate the thermodynamic phase equilibria as a function of TM ion content in the cathode material in the context of lithium nickel oxides, using a combined approach of first-principles density functional calculations, the cluster expansion method, and grand canonical Monte Carlo simulations. We developed a unified lattice Hamiltonian that accommodates not only rock-salt like structures but also topologically different spinel-like structures. Also, our model provides a foundation to investigate metastable cation compositions and kinetics of the phase transformations. Our investigations predict the existence of several Ni-rich phases that were, to date, unknown in the scientific literature. Our simulated phase diagrams at finite temperature show a very low solubility range of the prototype spinel phase. We find a partially disordered spinel-like phase with far greater solubility that is expected to show very different Li diffusivity compared to that of the prototype spinel structure.
Epitaxial growth of quadruple perovskite oxides presents an opportunity to expand their functionality and may lead to device applications. CeCu3Mn4O12 epitaxial thin film grown on YAlO3(110) exhibits ...a Neel temperature exceeding 400 K and metallic transport properties at room temperature, which can be accounted for by the high valence states of the constituting Ce4+ and Mn3.5+ stabilized by the oxidative deposition process. Uniaxial magnetic anisotropy is induced in CeCu3Mn4O12, whose easy axis lies parallel to orthorhombic YAlO310 where CeCu3Mn4O12 is most elongated. Perpendicular magnetic anisotropy can be realized in compressively strained CeCu3Mn4O12 by inserting a small YCaAlO4 buffer layer. This trend of magnetic anisotropy in strained CeCu3Mn4O12 was in good agreement with theoretical calculations.
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