Mao Yuliang, Zhong Jianxin
Institute for Quantum Engineering and Micro-Nano Energy Technology, Xiangtan University, Xiangtan 411105, Hunan, People's Republic of China. Center for Condensed Matter Physics, Faculty of Material and Photoelectronic Physics, Xiangtan University, Xiangtan 411105, Hunan, People's Republic of China.
Nanotechnology. 2008 May 21;19(20):205708. doi: 10.1088/0957-4484/19/20/205708. Epub 2008 Apr 15.
First-principles spin-polarized calculations have been conducted to investigate the structural, electronic and magnetic properties of 3d transition metal Mn doping into two typical sites in the upper layer of bilayer graphene with the AB Bernal structure. One of the doping sites is above the center of a carbon hexagon of the lower graphene layer (called the H site) and the other is directly on top of a carbon atom of the lower graphene layer (called the T site). We found that Mn doping enlarges the interlayer distance in bilayer graphene. Charge density distribution indicates that the region between the upper and lower graphene layer has apparent covalent-bonding characters due to the Mn doping. In the spin-polarized band structure of H site doping, the π and π(*) bands separate from each other at the Dirac point both in majority spin and minority spin. In the band structure of T site doping, the Fermi level is located above the Dirac point and moves to the conduction bands in majority spin and minority spin, making the bilayer graphene n doped. A high spin polarization of 95% is achieved due to the H site doping. The local moment of Mn for H and T site doping is reduced to 1.76 μ(B) and 1.88 μ(B), respectively, which are smaller than the value (5 μ(B)) in the free state.
已进行第一性原理自旋极化计算，以研究具有AB伯纳尔结构的双层石墨烯上层中两个典型位置掺入3d过渡金属Mn后的结构、电子和磁性特性。其中一个掺杂位置在下层石墨烯层的六边形碳中心上方（称为H位置），另一个直接位于下层石墨烯层的碳原子上方（称为T位置）。我们发现Mn掺杂会增大双层石墨烯的层间距。电荷密度分布表明，由于Mn掺杂，上下层石墨烯层之间的区域具有明显的共价键特征。在H位置掺杂的自旋极化能带结构中，π和π(*)能带在狄拉克点处，无论是多数自旋还是少数自旋都相互分离。在T位置掺杂的能带结构中，费米能级位于狄拉克点上方，且在多数自旋和少数自旋中都移动到导带，使双层石墨烯呈n型掺杂。由于H位置掺杂，实现了95%的高自旋极化。H和T位置掺杂时Mn的局域磁矩分别降至1.76 μ(B)和1.88 μ(B)，均小于自由状态下的值（5 μ(B)）。
