二维磁性材料Fe3GaTe2的磁性及自旋输运性质研究

二维van der Waals(vdW)磁性材料可构建单原子层自旋电子器件，通常具有强的磁各向异性和弱的层间耦合，为研究很多基础磁性现象提供了新的平台。磁性体系中的交换偏置现象(exchange bias)是磁存储的关键问题之一，但目前在二维vdW材料体系中只在远低于室温下观测到，这限制了其应用。最近发现的二维铁磁材料Fe₃GaTe₂有很强的垂直磁各向异性而且居里温度在室温以上，是研究二维体系交换偏置的理想材料。本论文首先生长了Fe₃GaTe₂单晶样品并研究了它们的物理性质，包括结构和磁性，然后基于机械剥离的纳米片制备了多个输运器件，并研究了这些纳米器件的输运性质。

通过单晶X射线衍射和透射电子显微镜研究发现生长的Fe₃GaTe₂具有较高的质量。磁性研究发现居里温度为350 K左右，室温下的饱和磁化强度为38.2 emu/g。在零场冷却的条件下测量的M-T曲线在250 K附近存在异常转变，我们认为这与单晶Fe₃GaTe₂的磁畴随温度的演变有关，并不代表样品中存在反铁磁相。

在二维Fe₃GaTe₂纳米片的输运研究中，我们首次观察到近室温(280 K)的交换偏置现象，该偏置现象可不经过场冷能自发产生，且偏置方向和大小可以通过扫场方式和扫场范围进行调控。本论文提出一个新的模型——交换弹簧模型，很好的解释了我们所有数据。Fe₃GaTe₂样品中存在矫顽场大的硬磁相和矫顽场小的软磁相，它们界面的交换弹簧作用导致了我们观察到的，可以用外磁场调控的磁滞偏置现象。

本论文中首次在二维vdW磁性材料中观察到近室温的交换偏置现象，并且提出一个新的交换弹簧模型进行了解释。此外，因为交换弹簧效应导致的偏置可以受外场调控，相比于传统的铁磁/反铁磁结构具有明显优势，这为构建磁性存储钉扎层提供了新的思路。

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