English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

The temperature dependence and anisotropy of optical spectral weightsassociated with different multiplet transitions is determined by the spin andorbital correlations. To provide a systematic basis to exploit this closerelationship between magnetism and optical spectra, we present and analyze thespin-orbital superexchange models for a series of representativeorbital-degenerate transition metal oxides with different multiplet structure.For each case we derive the magnetic exchange constants, which determine thespin wave dispersions, as well as the partial optical sum rules. The magneticand optical properties of early transition metal oxides with degenerate$t_{2g}$ orbitals (titanates and vanadates with perovskite structure) are shownto depend only on two parameters, viz. the superexchange energy $J$ and theratio $\eta$ of Hund's exchange to the intraorbital Coulomb interaction, and onthe actual orbital state. In $e_g$ systems important corrections follow fromcharge transfer excitations, and we show that KCuF$_3$ can be classified as acharge transfer insulator, while LaMnO$_3$ is a Mott insulator with moderatecharge transfer contributions. In some cases orbital fluctuations are quenchedand decoupling of spin and orbital degrees of freedom with static orbital ordergives satisfactory results for the optical weights. On the example of cubicvanadates we describe a case where the full quantum spin-orbital physics mustbe considered. Thus information on optical excitations, their energies,temperature dependence and anisotropy, combined with the results of magneticneutron scattering experiments, provides an important consistency test of thespin-orbital models, and indicates whether orbital and/or spin fluctuations areimportant in a given compound.Comment: 34 pages, 16 figure

Fingerprints of spin-orbital physics in cubic Mott insulators: Magnetic exchange interactions and optical spectral weights