电场调控亚铁磁合金异质结的磁性和自旋轨道矩效率

Spintronics devices manipulated by electric field are expected to realize high-speed, high-integration-density and low-power-consumption information storage and processing, where it is a key step for realistic application to achieve remarkable manipulation at room temperature through innovating material system. The present project proposes to carry out the research on the electrical manipulation of ferrimagnetic (FIM) heterojunctions. By utilizing the dramatic change of magnetism and spin orbit torque (SOT) efficiency at magnetization compensation point of FIM heterojunctions, giant manipulation degree is expected to realize. At first, high-quality FIM films (such as, Ta/CoTb) with perpendicular magnetic anisotropy are fabricated by co-sputtering technique. By changing the element ratio and temperature, we could verify the magnetization compensation point of the FIM alloy. Moreover, we would uncover the correlative mechanism between charge accumulation induced by electric field and intrinsic parameter (such as, carrier concentration, energy band structure, and density of state at fermi level) and clarify the mechanism of electric-field manipulation. Finally, we would use ion liquid as dielectric layer to construct gate-voltage-controllable device, which could effectively change the carrier density of FIM alloy. As a result, remarkably electric-field manipulation of the magnetization, coercive field, SOT efficiency, and critical switching current density could be observed. The research findings of this project not only benefit for clarifying the magnetoelectric coupling mechanism of FIM alloy, but also have potential application in low-power-consumption information storage and processing.

电场调控的自旋电子器件有望实现高速度、高集成度以及低功耗的信息处理和存储，其中通过革新材料体系实现室温下的大幅度调控是其迈向实际应用的关键步骤。本课题拟开展亚铁磁合金异质结的电场调控研究，利用其在磁矩补偿点附近磁性和自旋轨道矩效率的剧烈变化实现显著调控效果。首先，利用共溅射技术制备具有垂直磁各向异性的高品质亚铁磁合金异质结（例如，Ta/CoTb），并通过改变元素比例和温度确定亚铁磁合金的磁矩补偿点；然后，揭示电场引起的电荷积累与亚铁磁合金的载流子浓度、能带结构以及费米面态密度之间的关联，阐明电场调控的机制；最终，实验上制备出门电压调控器件，利用离子液体所形成的电解质双层调控亚铁磁合金的载流子浓度，实现电场对磁化强度、矫顽场、自旋轨道矩效率和临界翻转电流密度的显著调控。本项目的研究成果不仅有助于厘清亚铁磁合金内在的磁电耦合机理，而且在低功耗信息处理和存储方面有潜在应用价值。

电场调控的自旋电子器件有望实现高速度、高集成度以及低功耗的信息处理和存储，其中通过革新材料体系实现室温下的大幅度调控是其迈向实际应用的关键步骤。亚铁磁合金具有强的垂直磁各向异性和独特的磁补偿特性，并且在补偿点附近，亚铁磁合金的矫顽场、饱和磁化强度、自旋轨道矩效率等参数显著变化。因此，本课题利用上述亚铁磁合金的特性，开展了亚铁磁合金制备、物理机制分析以及电场调控三个方面研究，最终实现了磁特性参数的显著调控，项目所取得的创新性成果总结如下：.（1）本课题利用超高真空磁控溅射技术制备了高质量W/CoTb/Pt异质结，通过调节重金属层和亚铁磁合金的厚度实现强垂直磁各向异性，并在保证垂直磁各向异性的前提下，调控过渡族金属元素和稀土元素的比例，实现了从过渡族金属元素主导到稀土元素主导的一系列亚铁磁合金薄膜制备；.（2）通过系统理论研究，我们发现调控机制为电场驱动氢离子的嵌入和脱出，正电场作用下，氢离子逐渐嵌入亚铁磁合金，并与巡游电子结合，进而抑制稀土元素和过渡金属元素的磁矩大小，其中稀土元素磁矩受到更强烈的抑制，负电场作用下氢离子逐渐脱出，从而恢复初始状态。.（3）利用微纳加工技术将亚铁磁异质结制备成门电压调控器件，并利用电场实现对亚铁磁合金矫顽场、磁各向异性、磁补偿温度以及自旋轨道矩效率的大范围、非易失和可逆调控，其中磁补偿温度的调控幅度高达260K，并且实现了净磁矩的180°翻转。.机理研究方面，本项能够揭示功能离子与亚铁磁合金相互作用机制，厘清电场翻转亚铁磁合金净磁矩的微观机制，构建一种全新的磁矩翻转模式，为新型磁电耦合器件的设计与制备打开新思路。.实际应用方面，电场翻转磁矩的方式可以替代原有电流翻转磁矩方式，彻底消除焦耳热，极大的降低信息写入功耗，进而有望实现高密度、超低功耗的磁存储器件，并且电场调控自旋轨道矩效率增加了新的调控维度，可用于构建可重构的存算一体逻辑器件。