2014 Fiscal Year Research-status Report
Dynamics of Topological Textures in Antiferromagnetic Nanostructures
| Project/Area Number |
25800184
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| Research Institution | Tohoku University |
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Principal Investigator |
TRETIAKOV Oleg 東北大学, 金属材料研究所, 助教 (50643425)
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| Project Period (FY) |
2013-04-01 – 2016-03-31
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| Keywords | 反強磁性体 / 磁壁ダイナミクス / トポロジカルスピンテクスチャ |
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| Outline of Annual Research Achievements |
We derived and solved the system of coupled equations for the dynamics of a transverse antiferromagnetic (AFM) domain wall in AFM nanowire. The solutions of these equations allowed us to determine the drift velocity of this domain wall and to find the critical current. This current identifies the applicability limit of the LLG equation approach for AFMs.
We also studied for the first time the stability and dynamics of AFM skyrmions. Ferromagnetic skyrmions recently attracted a lot of attention because they are small in size and are better than domain walls at avoiding pinning while moved by electric current. Meanwhile, ferromagnetic skyrmions still have disadvantages such as the presence of stray fields and transverse dynamics, making them harder to employ for spintronic applications. In our current work, we have proposed a novel topological object: the AFM skyrmion. This topological texture has no stray fields and we show that its dynamics are faster compared to its ferromagnetic analogue. We obtain the dependence of AFM skyrmion radius on the strength of Dzyaloshinskii-Moriya interaction coming from relativistic spin-orbit effects and temperature. We find that the thermal properties, e.g. such as the AFM skyrmion radius and diffusion constant, are rather different from those for ferromagnetic skyrmions. More importantly, we show that due to unusual topology the AFM skyrmions do not have a velocity component transverse to the current and thus may be perfect candidates for spintronic applications.
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| Current Status of Research Progress |
Current Status of Research Progress
2: Research has progressed on the whole more than it was originally planned.
Reason
The generalized equations for the staggered field and magnetization dynamics, we derived earlier, allowed us to study current driven and magnetic field driven motion of transverse antiferromagnetic domain wall. We also studied for the first time stability and dynamics of antiferromagnetic skyrmions.
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| Strategy for Future Research Activity |
Derive and solve the system of coupled (LLG) equations for the dynamics in temperature gradients in AFM nanostructures. Use these solutions to determine the drift velocity of AFM topological defects.
Consider a possibility of spin-Seebeck effect in antiferromagnet/normal-metal structures. Here the role of normal metal will be played by such a material as Pt where the large spin-Hall angle would make sure good conversion of spin-current generated to a measurable electric voltage. Formulating and delivering the messages to the experimental community.
Assess the effects of the spin-orbit interactions on AFM skyrmions and their dynamics. Perform detailed study of AFM skyrmions with the Dzyaloshinskii-Moriya interaction and termperature effects.
Advanced considerations of combined effects of temperature gradients and electric currents (as well as magnetic fields). Comparison of obtained analytical results for simpler cases with the micromagnetic simulations.
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