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 Tools annual

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 monthly

Global: Zendy Plus monthly

Presents the access of premium content as premium feature

Premium Content

Global: Zendy Plus annual

Global: Zendy Free Plan

Two-dimensional (2D) magnetic materials are of current great interest fortheir promising applications in spintronics. Strong magnetic coupling andanisotropy are both highly desirable for the achievement of a high temperaturemagnetic order. Here we propose the unusual high valent FeS$_2$ hexagonalmonolayer as such a candidate for a strong Ising 2D ferromagnet (FM), byspin-orbital state analyses, first-principles calculations, and therenormalized spin-wave theory (RSWT). We find that very importantly, the highvalent Fe$^{4+}$ ion is in the low-spin state ($t_{2g}^{4}$, $S$=1) withdegenerate $t_{2g}$ orbitals rather than the high-spin state($t_{2g}^{3}e_g^{1}$, $S$=2). It is the low-spin state that allows to carry alarge perpendicular orbital moment and then produces a huge single ionanisotropy (SIA) of 25 meV/Fe. Moreover, the negative charge transfer characterassociated with the unusual high valence, strong Fe $3d$-S $3p$ hybridization,wide bands, and a small band gap all help to establish a strong superexchange.Indeed, our first-principles calculations confirm the strong FM superexchangeand the huge perpendicular SIA, both of which are further enhanced by acompressive strain. Then, our RSWT calculations predict that the FM $T_{\rm C}$is 261 K for the pristine FeS$_2$ monolayer and could be increased to 409 Kunder the compressive --5\% strain. The high $T_{\rm C}$ is also reproduced byour Monte Carlo (MC) simulations. Therefore, it is worth exploring thehigh-$T_{\rm C}$ Ising FMs in the high valent 2D magnetic materials withdegenerate orbitals.

FeS2 monolayer: a high valence and high-$T_{\rm C}$ Ising ferromagnet