Synthesis, structure and properties of layered phosphide nitrides $Ak$Th$_2$Mn$_4$P$_4$N$_2$ ($Ak$ = Rb, Cs)

TL;DR

This paper reports the synthesis, structural analysis, and property measurements of layered phosphide nitrides $Ak$Th$_2$Mn$_4$P$_4$N$_2$ ($Ak$ = Rb, Cs), revealing their complex layered structure, intrinsic hole doping, magnetic properties, and strong electron correlations.

Contribution

It introduces new layered phosphide nitrides with unique intergrowth structures, demonstrating their magnetic and electronic properties through experimental and first-principles studies.

Findings

Presence of local moments and itinerant electrons.

Antiferromagnetic interactions with enhanced d-p hybridizations.

Strong electron correlations indicated by density of states analysis.

Abstract

We report the design, synthesis, structure, and properties of two complex layered phosphide nitrides, $Ak$Th$_2$Mn$_4$P$_4$N$_2$ ($Ak$ = Rb, Cs), which contain anti-fluorite-type [Mn$_2$P$_2$] bilayers separated by fluorite-type [Th2N2] layers as a result of the intergrowth between AkMn$_2$P$_2$ and ThMnPN. The new compounds are featured with an intrinsic hole doping associated with the interlayer charge transfer and a built-in chemical pressure from the [Th$_2$N$_2$] layers, both of which are reflected by the changes in the lattice and the atomic position of phosphorus. The measurements of magnetic susceptibility, electrical resistivity, and specific heat indicate existence of local moments as well as itinerant electrons in relation with d-p hybridizations. The expected dominant antiferromagnetic interactions with enhanced d-p hybridizations were demonstrated by the first-principles calculations only when additional Coulomb repulsions are included. The density of states at the Fermi level derived from the specific-heat analysis are 3.5 and 7.5 times of the calculated ones for Ak = Rb and Cs, respectively, suggesting strong electron correlations in the title compounds.