Cr_(1+δ)Te₂ are pseudo-layered compounds consisting of CrTe₂ transition metal dichalcogenide (TMD) layers with additional (δ) self-intercalated Cr atoms. The recent search for ferromagnetic 2D materials revived the interest into chromium tellurides. Here, Cr_(1+δ)Te₂ nanolayers are epitaxially grown on MoS₂ (0001), forming prototypical van der Waals heterostructures. Under optimized growth conditions, ultrathin films of only two TMD layers with a single intercalated Cr-layer are achieved, forming a 2D sheet with van der Waals surfaces. Detailed compositional and structural characterization by scanning tunneling microscopy, grazing incidence x-ray diffraction, and high-resolution Rutherford backscattering indicate the layer-by-layer growth and that the δ can be tuned by post-growth annealing in a range between ∼0.5 and 1. X-ray magnetic circular dichroism and magnetometry measurements demonstrate that all self-intercalated Cr_(1+δ)Te₂ nanolayers exhibit strong ferromagnetism with magnetic moments larger than 3μ_B per Cr-atom. The magnetic properties are maintained in the ultrathin limit of a material with a single intercalation layer. Interestingly, the magnetic anisotropy can be tuned from close to isotropic (δ = 1) to a desirable perpendicular anisotropy for low δ values. Thus, the bottom-up growth of these 2D Cr_(1+δ)Te₂ sheets is a promising approach for designing magnetic van der Waals heterostructures.

中文翻译：

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具有浓度可调磁各向异性的二维铁磁 Cr(1+δ)Te2 纳米层的范德华外延生长

Cr _(1+δ) Te ₂是由CrTe ₂过渡金属二硫属化物(TMD)层和额外的(δ)自嵌入Cr原子组成的假层状化合物。最近对铁磁二维材料的研究重新唤起了人们对碲化铬的兴趣。这里，Cr _(1+δ) Te _{2纳米层在 MoS 2}上外延生长（0001），形成原型范德华异质结构。在优化的生长条件下，实现了只有两个 TMD 层和一个单层插入 Cr 层的超薄膜，形成了具有范德华表面的二维片材。通过扫描隧道显微镜、掠入射 X 射线衍射和高分辨率卢瑟福背散射进行详细的成分和结构表征，表明逐层生长，并且 δ 可以通过生长后退火在 ~0.5 和1. X射线磁圆二色性和磁力测量表明，所有自插层Cr _(1+δ) Te ₂纳米层都表现出强铁磁性，磁矩大于3 μ _B每个 Cr 原子。磁性保持在具有单个插层的材料的超薄极限内。有趣的是，磁各向异性可以从接近各向同性（δ = 1）调整为低 δ 值的理想垂直各向异性。_{因此，这些 2D Cr (1+δ)} Te ₂片材的自下而上生长是设计磁性范德华异质结构的有前景的方法。