From ferromagnetic semiconductor to anti-ferromagnetic metal in epitaxial Cr${}_x$Te${}_y$ monolayers

Abstract

Chromium ditelluride, CrTe${}_2$, is an attractive candidate van der Waals material for hosting 2D magnetism. However, how the room-temperature ferromagnetism of the bulk evolves as the sample is thinned to the single-layer limit has proved controversial. This, in part, reflects its metastable nature, vs. a series of more stable self-intercalation compounds with higher relative Cr:Te stoichiometry. Here, exploiting a recently-developed method for enhancing nucleation in molecular beam epitaxy growth of transition-metal chalcogenides, we demonstrate the selective stabilisation of high-coverage CrTe${}_2$ and Cr${}_{2+\epsilon }$Te${}_3$ epitaxial monolayers. Combining X-ray magnetic circular dichroism, scanning tunnelling microscopy, and temperature-dependent angle-resolved photoemission, we demonstrate that both compounds order magnetically with a similar Tc. We find, however, that monolayer CrTe${}_2$ forms as an anti-ferromagnetic metal, while monolayer Cr${}_{2+\epsilon }$Te${}_3$ hosts an intrinsic ferromagnetic semiconducting state. This work thus demonstrates that control over the self-intercalation of metastable Cr-based chalcogenides provides a powerful route for tuning both their metallicity and magnetic structure, establishing the Cr-Te system as a flexible materials class for future 2D spintronics.

References in corpus (9)

• Quantum ESPRESSO: a modular and open-source software project for quantum simulations of materials
• Advanced capabilities for materials modelling with Quantum ESPRESSO
• From Stoner to Local Moment Magnetism in Atomically Thin Cr2Te3
• Morphology Control of Epitaxial Monolayer Transition Metal Dichalcogenides
• Orbital-selective Band Hybridisation at the Charge Density Wave Transition in Monolayer TiTe${}_2$
• Noncollinear magnetism in two-dimensional CrTe${}_2$
• Covalency, correlations, and inter-layer interactions governing the magnetic and electronic structure of Mn${}_3$Si${}_2$Te${}_6$
• Uncovering the lowest thickness limit for room-temperature ferromagnetism of Cr${}_{1.6}$Te${}_2$
• Charge doping into spin minority states mediates doubling of $T_{\mathrm{C}}$ in ferromagnetic CrGeTe${}_3$

Cited by in corpus (4)

• Electronic structure of monolayer-CrTe${}_2$: an antiferromagnetic 2D van der Waals material
• Substrate pre-sputtering for layer-by-layer van der Waals epitaxy of 2D materials
• Many-body electronic structure, self-doped double-exchange, and Hund metallicity in 1T-CrTe2 bulk and monolayer
• Competing magnetic phases in Cr${}_{3+\delta }$Te${}_4$ are spatially segregated