Institute of Physics and Technology, Ural Federal University, Yekaterinburg, Russia.
Nanoscale. 2018 Jun 14;10(23):11186-11195. doi: 10.1039/c8nr02328j.
The study of magnetism without the involvement of transition metals or rare earth ions is considered the key to the fabrication of next generation spintronic devices. Several recent reports claim that optimizing the occupation number of the mixed p-orbitals is the correct way to reinforce p-orbital magnetism in bulk crystals. We provide experimental evidence that the kinked monoatomic carbon chains, the so-called linear-chained carbon, generate intrinsic ferromagnetism even above room temperature. According to our ab initio calculations, unconventional magnetism has its origin in the p-shells. In contrast, the linear monoatomic carbon chains are non-magnetic. Although the optimized differential spin density of states at the Fermi level (SDOS) of the kinked carbon chains is higher than that of bulk Fe, the magnetic moment is as low as 0.3μB. In order to enhance the magnetic response, we decided to tune the p-orbital magnetism by adding dopants from groups IV to VII of the periodic table. We observed that the strength of the p-orbital magnetism and the sign of the exchange interaction depend not only on the kink angle, but also on the concentration of lone pair electrons, free radical electrons, lateral chain spacing, internal electric dipole, dative covalent bonds and the Bohr radius of the dopants. Surprisingly, the V and VII-doped carbon chains show a strong non-zero SDOS, which has its origin in the p-shells. The VII-doped carbon chains give the SDOS of the opposite sign. Our best system, the arsenic-doped carbon chain, exhibits a strong local magnetic moment of 1.5μB, which is comparable to that of the bulk Fe of 2.2μB, with the mean exchange-correlation energy reaching a 63% ratio relative to that of the bulk Fe.
没有过渡金属或稀土离子参与的磁性研究被认为是制造下一代自旋电子器件的关键。最近有几份报告声称，优化混合 p 轨道的占据数是增强体相晶体中 p 轨道磁性的正确方法。我们提供了实验证据，证明所谓的线性链式碳中的弯曲单原子碳链在室温以上就能产生本征铁磁性。根据我们的从头算计算，非常规磁性源于 p 壳层。相比之下，线性单原子碳链是无磁性的。尽管弯曲碳链在费米能级的差分自旋态密度（DOS）优化值高于体相 Fe，但磁矩却低至 0.3μB。为了增强磁响应，我们决定通过添加来自元素周期表 IV 族到 VII 族的掺杂剂来调节 p 轨道磁性。我们观察到，p 轨道磁性的强度和交换相互作用的符号不仅取决于弯曲角，还取决于孤对电子、自由基电子、侧链间距、内部电偶极、配位共价键和掺杂剂的玻尔半径的浓度。令人惊讶的是，V 和 VII 掺杂的碳链表现出强烈的非零 SDOS，其起源于 p 壳层。VII 掺杂的碳链给出了相反符号的 SDOS。我们的最佳体系，砷掺杂的碳链，表现出 1.5μB 的强局域磁矩，与体相 Fe 的 2.2μB 相当，平均交换相关能量达到体相 Fe 的 63%。
