BaZrS3 is a prototypical chalcogenide perovskite, an emerging class of unconventional semiconductor. Recent results on powder samples reveal that it is a material with a direct band gap of 1.7-1.8 eV, a very strong light-matter interaction, and a high chemical stability. Due to the lack of quality thin films, however, many fundamental properties of chalcogenide perovskites remain unknown, hindering their applications in optoelectronics. Here we report the fabrication of BaZrS3 thin films, by sulfurization of oxide films deposited by pulsed laser deposition. We show that these films are n-type with carrier densities in the range of 10 19 -10 20 cm -3 . Depending on the processing temperature, the Hall mobility ranges from 2.1 to 13.7 cm 2 /Vs. The absorption coefficient is > 10 5 cm -1 at photon energy > 1.97 eV. Temperature dependent conductivity measurements suggest shallow donor levels. By assuring that BaZrS3 is a promising candidate, these results potentially unleash the family of chalcogenide perovskites for optoelectronics such as photodetectors, photovoltaics, and light emitting diodes.

The development of intrinsic ferromagnetism in two-dimensional (2D) limit is at the core of ultra-compact spintronic applications. However, direct synthesis of non-layered 2D magnets with strong ferromagnetic order is still in infancy. Here we report the phasecontrollable synthesis of trigonal and monoclinic Cr5Te8 flakes via a facile chemical vapor deposition route. Both phases exhibit robust ferromagnetism with strong perpendicular anisotropy down to a few nanometers, as confirmed by both magneto-optical and 2 magnetotransport measurements. High Curie temperature up to 200 K is obtained by manipulating the phase structure and thickness. Remarkably, a colossal anomalous Hall effect is observed in the more distorted monoclinic Cr5Te8 with an enhanced anomalous Hall conductivity of 650 Ω -1 cm -1 and anomalous Hall angle of 5% achieved simultaneously. Our work paves the way for the scalable synthesis of 2D magnetic materials and highlights the great potential of Cr5Te8 for engineering future spintronic devices.

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MnBi 2 Te 4 is an antiferromagnetic topological insulator that has stimulated intense interest due to its exotic quantum phenomena and promising device applications. The surface structure is a determinant factor to understand the magnetic and topological behavior of MnBi 2 Te 4 , yet its precise atomic structure remains elusive. Here we discovered a surface collapse and reconstruction of few-layer MnBi 2 Te 4 exfoliated under delicate protection. Instead of the ideal septuple-layer structure in the bulk, the collapsed surface is shown to reconstruct as a Mn-doped Bi 2 Te 3 quintuple layer and a Mn x Bi y Te double layer with a clear van der Waals gap in between. Combined with first-principles calculations, such surface collapse is attributed to the abundant intrinsic Mn−Bi antisite defects and the tellurium vacancy in the exfoliated surface, which is further supported by in situ annealing and electron irradiation experiments. Our results shed light on the understanding of the intricate surface-bulk correspondence of MnBi 2 Te 4 and provide an insightful perspective on the surface-related quantum measurements in MnBi 2 Te 4 few-layer devices.

Intrinsic antiferromagnetism in van der Waals (vdW) monolayer (ML) crystals enriches our understanding of two-dimensional (2D) magnetic orders and presents several advantages over ferromagnetism in spintronic applications. However, studies of 2D intrinsic antiferromagnetism are sparse, owing to the lack of net magnetisation. Here, by combining spin-polarised scanning tunnelling microscopy and first-principles calculations, we investigate the magnetism of vdW ML CrTe2, which has been successfully grown through molecular-beam epitaxy. We observe a stable antiferromagnetic (AFM) order at the atomic scale in the ML crystal, whose bulk is ferromagnetic, and correlate its imaged zigzag spin texture with the atomic lattice structure. The AFM order exhibits an intriguing noncollinear spin reorientation under magnetic fields, consistent with its calculated moderate magnetic anisotropy. The findings of this study demonstrate the intricacy of 2D vdW magnetic materials and pave the way for their in-depth analysis.