In-Plane Ferromagnetism and Critical Dynamics in Alkali-Deficient K${}_{1-x}$CrTe${}_2$ (with $x\approx$ 0.3) Single Crystals

Abstract

Layered chromium tellurides are model systems for studying low-dimensional magnetism in van der Waals materials. We report the synthesis and characterization of K${}_{1-x}$CrTe${}_2$ single crystals ($x\approx 0.3$), which crystallize in the $Cm$ space group with trigonal prismatic K${}^{+}$ coordination, unlike the octahedral environments of more stoichiometric ACrX${}_2$ compounds. Magnetization measurements show a sharp ferromagnetic transition at $T_{\mathrm{C}}=117$ K and in-plane magnetic anisotropy, supported by density functional theory. Neutron diffraction reveals ferromagnetic alignment of Cr spins within and between layers. This contrasts with the out-of-plane A-type antiferromagnetism in LiCrTe${}_2$ and NaCrTe${}_2$, but resembles CrTe${}_2$. These differences likely arise from changes in interlayer spacing, Cr oxidation state, or stacking. AC susceptibility and $\mu$SR indicate short-range order above $T_{\mathrm{C}}$ and dynamic behavior below. Overall, K${}_{1-x}$CrTe${}_2$ provides a tunable platform for studying spin orientation and dimensionality in two-dimensional magnets.

35 pages, 8 figures