Jiang Shengwei, Li Lizhong, Wang Zefang, Mak Kin Fai, Shan Jie
School of Applied and Engineering Physics, Cornell University, Ithaca, NY, USA.
Laboratory of Atomic and Solid State Physics, Cornell University, Ithaca, NY, USA.
Nat Nanotechnol. 2018 Jul;13(7):549-553. doi: 10.1038/s41565-018-0135-x. Epub 2018 May 7.
The atomic thickness of two-dimensional materials provides a unique opportunity to control their electrical and optical properties as well as to drive the electronic phase transitions by electrostatic doping. The discovery of two-dimensional magnetic materials has opened up the prospect of the electrical control of magnetism and the realization of new functional devices. A recent experiment based on the linear magneto-electric effect has demonstrated control of the magnetic order in bilayer CrI by electric fields. However, this approach is limited to non-centrosymmetric materials magnetically biased near the antiferromagnet-ferromagnet transition. Here, we demonstrate control of the magnetic properties of both monolayer and bilayer CrI by electrostatic doping using CrI-graphene vertical heterostructures. In monolayer CrI, doping significantly modifies the saturation magnetization, coercive force and Curie temperature, showing strengthened/weakened magnetic order with hole/electron doping. Remarkably, in bilayer CrI, the electron doping above ~2.5 × 10 cm induces a transition from an antiferromagnetic to a ferromagnetic ground state in the absence of a magnetic field. The result reveals a strongly doping-dependent interlayer exchange coupling, which enables robust switching of magnetization in bilayer CrI by small gate voltages.
二维材料的原子厚度为控制其电学和光学性质以及通过静电掺杂驱动电子相变提供了独特的机会。二维磁性材料的发现开启了磁学的电学控制以及新型功能器件实现的前景。最近基于线性磁电效应的一项实验证明了电场对双层CrI中磁序的控制。然而，这种方法仅限于在反铁磁 - 铁磁转变附近磁偏置的非中心对称材料。在此，我们展示了使用CrI - 石墨烯垂直异质结构通过静电掺杂对单层和双层CrI的磁性进行控制。在单层CrI中，掺杂显著改变了饱和磁化强度、矫顽力和居里温度，随着空穴/电子掺杂显示出增强/减弱的磁序。值得注意的是，在双层CrI中，在没有磁场的情况下，高于约2.5×10¹³ cm⁻²的电子掺杂会诱导从反铁磁基态到铁磁基态的转变。该结果揭示了一种强烈依赖于掺杂的层间交换耦合，这使得通过小的栅极电压就能在双层CrI中实现稳健的磁化切换。
