Structural Modulation and Enhanced Magnetic Ordering in Incommensurate K$_{1-{x}}$CrSe$_2$ Crystals

TL;DR

This study reports the discovery of an incommensurately modulated K$_{1-x}$CrSe$_2$ crystal with enhanced magnetic ordering, achieved through structural modulation, which could enable tuning magnetic properties in layered materials.

Contribution

First synthesis of K$_{1-x}$CrSe$_2$ with incommensurate modulation and detailed analysis of its structure and magnetic behavior.

Findings

Incommensurate modulation compensates for K deficiency.

Magnetic transition occurs at 133 K, higher than previous compounds.

Structural modulation influences magnetic ordering.

Abstract

Layered delafossite-type compounds and related transition metal dichalcogenides, characterized by their triangular net structures, serve as prototypical systems for exploring the intricate interplay between crystal structure and magnetic behavior. Herein, we report on the discovery of the compound K$_{1-x}$CrSe$_2$ ($x \approx$ 0.13), an incommensurately modulated phase. Single crystals of this compound were grown for the first time using a K/Se self-flux. We find a monoclinic crystal structure with incommensurate modulation, that can be rationalized by a 3+1 dimensional model. This modulation compensates for the under-stoichiometry of K cations, creating pronounced undulations in the CrSe$_2$ layers. Our anisotropic magnetization measurements reveal that K$_{1-x}$CrSe$_2$ undergoes a transition to a long-range magnetically ordered state below $T_{\mathrm N}$ = 133 K, a temperature 1.6 to 3.3 times higher than in earlier reported KCrSe$_2$ compounds. Our findings open new avenues for tuning the magnetic properties of these layered materials through structural modulation.