Magnetic van der Waals (vdW) materials are the centerpiece of atomically thin devices with spintronic and optoelectronic functions. Exploring new chemistry paths to tune their magnetic and optical properties enables significant progress in fabricating heterostructures and ultracompact devices by mechanical exfoliation. The key parameter to sustain ferromagnetism in 2D is magnetic anisotropy—a tendency of spins to align in a certain crystallographic direction known as easy‐axis. In layered materials, two limits of easy‐axis are in‐plane (XY) and out‐of‐plane (Ising). Light polarization and the helicity of topological states can couple to magnetic anisotropy with promising photoluminescence or spin‐orbitronic functions. Here, a unique experiment is designed to control the easy‐axis, the magnetic transition temperature, and the optical gap simultaneously in a series of CrCl_3−xBr_x crystals between CrCl₃ with XY and CrBr₃ with Ising anisotropy. The easy‐axis is controlled between the two limits by varying spin–orbit coupling with the Br content in CrCl_3−x Br_x. The optical gap, magnetic transition temperature, and interlayer spacing are all tuned linearly with x. This is the first report of controlling exchange anisotropy in a layered crystal and the first unveiling of mixed halide chemistry as a powerful technique to produce functional materials for spintronic devices.

中文翻译：

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通过混合卤化物化学控制范德华晶体CrCl3-xBrx的磁性和光学性质

范德华（vdW）磁性材料是具有自旋电子和光电功能的原子薄型设备的核心。探索新的化学途径以调节其磁性和光学性质，使得通过机械剥离制造异质结构和超紧凑设备的工作取得了重大进展。维持2D方向铁磁性的关键参数是磁各向异性-自旋倾向在称为易轴的特定晶体学方向上排列的趋势。在分层材料中，易轴的两个限制是面内（XY）和平面外（Ising）。光的极化和拓扑状态的螺旋度可以与具有光致发光或自旋或双电子功能的磁各向异性耦合。在这里，一个独特的试验被设计成同时控制易磁化轴，磁转变温度和光学带隙的一系列的CrCl的_{3- X}溴_X的CrCl之间晶体₃与XY和CrBr ₃与伊辛各向异性。通过改变自旋轨道耦合与CrCl _{3− x} Br _x中的Br含量，可以在两个极限之间控制易轴。光学间隙，磁性转变温度和中间层间距均通过X。这是第一个控制层状晶体中交换各向异性的报告，也是混合卤化物化学作为生产自旋电子器件功能材料的有力技术的首次公开报道。