石墨烯锯齿型晶界局域态的磁性和自旋传输特性研究

石墨烯有很长的自旋寿命和自旋扩散长度，是理想的自旋电子学材料，但是石墨烯是抗磁体，如何有效地引入自旋是该领域的重要问题。理论研究表明锯齿型晶界局域态可以实现磁长程有序并产生自旋过滤效应，但尚未有相关实验报道。申请人已可控制备出具有锯齿型晶界的石墨烯，证实了晶界局域态的存在，从理论上展示了自旋过滤效应。鉴于此，本项目将以锯齿型晶界石墨烯为研究对象，通过掺杂、晶界磁耦合等手段来调控磁有序；通过测量逆自旋霍尔效应研究电子垂直隧穿晶界的自旋流密度，阐述自旋轨道耦合和横向偏压对自旋过滤效应的调制；通过测量电子垂直隧穿两个具有反铁磁耦合晶界的磁电阻，研究磁场和自旋极化电流对晶界磁矩的反转；通过测量基于磁铁/势垒层的非局域磁电阻，研究晶界对自旋的驰豫。本项目的实施，预期将实现铁磁石墨烯；构筑基于单个晶界的自旋过滤器和基于两个晶界磁耦合的原子层厚度自旋阀；为设计和构筑全碳自旋器件奠定实验基础。

Graphene has long spin life times and long diffusion lengths at room temperature, making it highly promising for spintronics. However, pristine graphene is diamagnetic and making graphene magnetic remains a principal challenge. It was shown by theoretical studies that graphene zig-zag grain boundaries with localized states can form long magnetic ordering and work as spin-filtering. However, there is no experimental report so far. Applicant has prepared graphene with zig-zag grain boundaries in a controllable way, experimentally confirmed the presence of the localized states, and also theoretically demonstrated the spin-filtering effect. In this project, we will continue to investigate the magnetic and spin-dependent transport properties of graphene with zig-zag boundaries. We will form and improve long magnetic ordering using elements doping and magnetic coupling of grain boundaries. We will also plan to confirm the spin-filtering effect of single grain boundary by measuring the spin current crossing grain boundary based on inverse spin hall effect and demonstrate how spin-filter effect is affected by spin-orbit coupling and bias voltage. We will also intent to measure the magneto-resistance of electrons crossing two antiferromagnetic coupled grain boundaries and investigate how to rotate magnetic moments of graphene boundary with magnetic field and spin-polarized current. We also plan to study the spin relaxation induced by grain boundary through measuring the nonlocal magneto-resistance based on devices with ferromagnet/tunnel barrier. Through the implementation of this project, we will make ferromagnetic graphene, design the spin-filter based on single grain boundary, and fabricate atomic thick spin valve based on two magnetic coupled grain boundaries.