Extreme Air Sensitivity and Nonself-Limited Oxidation of Two-Dimensional Magnetic Tellurides

Abstract

The two-dimensional (2D) self-intercalated van der Waals magnets, chromium tellurides (Cr1+δTe2), with room temperature ferromagnetism and exotic topological spin textures, have emerged as an attractive platform for the development of ultrathin spintronic devices. While many prior studies claim Cr1+δTe2 are air-stable, which is crucial for practical applications, we demonstrate that within only minutes of exposure to air dramatic changes occur in the Raman and X-ray photoelectron spectroscopy spectra of nanoplates at room temperature. Time-dependent magnetization measurements and transmission electron microscopy studies suggested the rapid oxidation is not self-limited and has distinct processes on the surfaces and edges. Density functional theory calculations confirmed the spontaneous oxygen adsorption on the surface and the thermodynamically favorable oxidation process. These findings demonstrate unambiguously that the surface of Cr1+δTe2 is extremely air-sensitive, highlighting the necessity of surface protection for fundamental studies of intrinsic 2D magnetism and practical applications of advanced spintronic devices.