Controllable CVD Growth of 2D Cr5Te8 Nanosheets with Thickness-Dependent Magnetic Domains

As a unique 2D magnetic material with self-intercalated structure, Cr₅Te₈ exhibits many intriguing magnetic properties. While its ferromagnetism of Cr₅Te₈ has been previously reported, the research on its magnetic domain remains unexplored. Herein, we have successfully fabricated 2D Cr₅Te₈ nanosheets with controlled thickness and lateral size by chemical vapor deposition (CVD). Then magnetic property measurement system revealed Cr₅Te₈ nanosheets exhibiting intense out-of-plane ferromagnetism with a Curie temperature (T_C) of 176 K. Significantly, we reported for the first time two magnetic domains: magnetic bubbles and thickness-dependent maze-like magnetic domains in our Cr₅Te₈ nanosheets by cryogenic magnetic force microscopy (MFM). The domain width of the maze-like magnetic domains increases rapidly with decreasing sample thickness; meanwhile, the domain contrast decreases. This indicates the dominant role of ferromagnetism shifts from dipolar interactions to magnetic anisotropy. Our research not only establishes a pathway for the controllable growth of 2D magnetic materials but also points toward novel avenues for regulating magnetic phases and methodically tuning domain characteristics.

Controlled Synthesis of a Two-Dimensional Non-van der Waals Ferromagnet toward a Magnetic Moiré Superlattice

Two-dimensional (2D) magnetic materials provide an ideal platform for spintronics, magnetoelectrics, and numerous intriguing physical phenomena in 2D limits. Moiré superlattices based on 2D magnets offer an avenue for controlling the spin degree of freedom and engineering magnetic properties. However, the synthesis of high-quality, large-grain, and stable 2D magnets, much less obtaining a magnetic moiré superlattice, is still challenging. We synthesize 2D ferromagnets (trigonal Cr₅Te₈) with controlled thickness and robust stability through chemical vapor deposition. Single-unit-cell-thick flakes with lateral sizes of tens of micrometers are obtained. We observe the layer-by-layer growth mode for the crystal formation in non-van der Waals Cr₅Te₈. The robust anomalous Hall signal confirms that Cr₅Te₈ of varying thickness have a long-range ferromagnetic order with an out-of-plane easy axis. There is no obvious change of the Curie temperature when the thickness of Cr₅Te₈ decreases from 52.1 to 7.2 nm. Here, we construct diverse 2D non-van der Waals/van der Waals vertical heterostructures (Cr₅Te₈/graphene, Cr₅Te₈/h-BN, Cr₅Te₈/MoS₂). A uniform moiré superlattice is formed in the heterostructure through a lattice mismatch. The successful growth of 2D Cr₅Te₈ and a related moiré superlattice introduces 2D non-van der Waals ferromagnets into moiré superlattice research, thus highlighting prospects for property investigation of a non-van der Waals magnetic moiré superlattice and massive applications which require a scalable approach to magnetic moiré superlattices.

Insight into intrinsic ferromagnetism in quasi-2D Cr5-yTe8

Cr₅Te₈is a half metal with 2D van der Waals ferromagnetic structure and its magnetic properties can be tuned by changing the proportionality of Cr and Te. We report an investigation of magnetization and magnetic anisotropy near the critical transition region of a Cr_5-yTe₈single crystal with the static and dynamic probes, to unravel the nature of field-dependent spin-spin interactions. The magnetic transition temperatureT_Cincreasing from 255 K (at near zero-field) to 279 K (at 65 kOe along theab-plane) has been identified. Accordingly, a phase diagram of field versus transition temperature has been established. From the analysis of the field dependence of the critical behavior, we provided evidence that the scenario of 2D Heisenberg-type interactions can be employed to interpret the field-dependent magnetic transitions in Te-rich Cr_4.8Te₈. The precise picture for the field-reduced spin-spin interaction range has been obtained. The conclusion drawn from the present study demonstrated that Cr_4.8Te₈is a promising candidate for the spintronic applications with a tunable magnetic transition temperature.