科研之友
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摘要
Spintronics, using spins of electrons for the information transmission, process and storage, which is a promising technology in the future. Low-dimensional materials, with strong quantum effect, is an ideal platform for the study of spin-charge interactions and could be utilized as spintronics devices. So far, due to the excess freedoms provided by defect, impurity, interface and boundary effects, the magnetic systems with long-range order are difficult to obtain and manipulate. Exploring novel materials in low-dimensional remains a big challenge. In recent years, based on the well-developed first-principle calculations, together with the classical physical model, it's efficient to predict the critical phenomena in low-dimensional materials accurately, which can provide the insights into the spintronics. Moreover, the hybrid and more advanced calculation methods are utilized as effective to understand the electronic structures of strongly correlated systems with consideration of the coulomb interaction between the local d or f electrons. Plus, the magnetic anisotropic energy is also calculated to confirm the easy-magnetization axis, which could be useful to determine the moderate interaction models and further to anticipate the critical behavior in ferromagnetic or antiferromagnetic systems. To utilize the low-dimensional spintronics above room-temperature, high critical transition temperature is prerequisite and in other words, the coupling mechanism matters. Here, through the overview of the recent low-dimensional researches, the highly reliable low-dimensional spintronics are summarized and their exchange interactions are discussed. For one-dimensional spintronics, ligand-H saturated 3d metal chains and MOF-like organic systems are introduced. The mechanical and thermodynamic stabilities are validated and electronic properties shows that the ground states are ferromagnetic or antiferromagnetic, which both own the high magnetization anisotropic energy. Unlike the benzene-ligand ferromagnetic chains, hydrogen can bring the direct interaction into one-dimensional chains and further modulate the transmission properties at the same time. The direct exchange interaction can be a better way to remain the magnetic states. Another MOF-like chains, the exchange interactions are through the basal plane of carbon materials, which could be a super-long exchange interaction. For two-dimensional materials, the CrI 3 and Cr 2 Ge 2 Te 6 are narrowed down to monolayer successfully and they are both ferromagnetic, which the critical transition behaviors can be reproduced using Ising or XY model. Besides, the high throughput calculations are carried out to screen the potential two-dimensional spintronics. However, the understanding of the exchange interactions which is important for keeping the ferromagnetic or antiferromagnetic states is rare. In the Fe-Si alloy systems, a possible two-dimensional system is designed and the ground states is ferromagnetic. Additionally, it is half-metallic and the curie temperature can reach up to 780 K, which is a promising candidate to investigate the two-dimensional spintronics and potential is applications. Other recent calculations also show that through the W-dopant in CrI 3 or Cr 2 Ge 2 Te 6 , the curie temperature can be improved, which originates from the narrowing of virtual gaps between orbitals and enhances the coupling interactions. At last, the modulation of spintronics through magnetic fields is difficult for the device miniaturization. Hence, using the electronic field is more convenient and a novel spintronics called bipolar magnetic semiconductor is introduced as a potential material for spintronics. Some other methods like strain and carrier doping could also be utilized to regulate the intrinsic magnetic behaviors reversely.
- 出版日期2018
- 单位中国科学技术大学
