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 Plus monthly

Global: Zendy Tools annual

Global: Zendy Tools monthly

Global: Zendy Free Plan

CaCu$_3$Fe$_4$O$_{12}$ exhibits a temperature-induced transition from aferrimagnetic-insulating phase, in which Fe appears charge disproportionated,as Fe$^{3+}$ and Fe$^{5+}$, to a paramagnetic-metallic phase at temperaturesabove 210 K, with Fe$^{4+}$ present. To describe it, we propose a microscopiceffective model with two interpenetrating sublattices of Fe$^{(4-\delta)+}$ andFe$^{(4+\delta)+}$, respectively, being $\delta$ the Fe-chargedisproportionation. We include all $3d$-Fe orbitals: $t_{2g}$ localizedorbitals, with spin 3/2 and magnetically coupled, plus two degenerate itinerant$e_g$ orbitals with local and nearest-neighbor (NN) electron correlations, andhopping between NN $e_g$ orbitals of the same symmetry. Allub and Alasciopreviously proposed a model to describe the phase transition inLaCu$_3$Fe$_4$O$_{12}$ from a paramagnetic-metal to anantiferromagnetic-insulator, induced by temperature or pressure, involvingcharge transfer between Fe and Cu ions, in contrast to Fe-chargedisproportionation. With the model proposed for CaCu$_3$Fe$_4$O$_{12}$,modified to account for this difference between the two compounds, the densityof states of the itinerant Fe orbitals was obtained, using Green's functionsmethods. The phase diagram for CaCu$_3$Fe$_4$O$_{12}$ was calculated, includingphases exhibiting Fe-charge disproportionation, where the two eg orbitals ineach site are symmetrically occupied, as well as novel phases exhibiting localorbital selectivity/asymmetric occupation of $e_g$ orbitals. Both kinds ofphases may exhibit paramagnetism and ferromagnetism. We determined the modelparameters which best describe the phase transition observed inCaCu$_3$Fe$_4$O$_{12}$, and found other phases at different parameter ranges,which might be relevant for other compounds of the ACu$_3$Fe$_4$O$_{12}$family, which present both types of transitions.

Phase diagram description of the CaCu$_3$Fe$_4$O$_{12}$ double perovskite