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Domain wall of a ferromagnet on a three-dimensional topological insulator.

Wakatsuki R, Ezawa M, Nagaosa N - Sci Rep (2015)

Bottom Line: Most of them come from the peculiar surface or edge states.Especially, the quantized anomalous Hall effect (QAHE) without an external magnetic field is realized in the two-dimensional ferromagnet on a three-dimensional TI which supports the dissipationless edge current.The chirality and relative stability of the Neel wall and Bloch wall depend on the position of the Fermi energy as well as the form of the coupling between the magnetic moments and orbital of the host TI.

View Article: PubMed Central - PubMed

Affiliation: Department of Applied Physics, University of Tokyo, 7-3-1, Hongo, Bunkyo-ku, Tokyo 113-8656, Japan.

ABSTRACT
Topological insulators (TIs) show rich phenomena and functions which can never be realized in ordinary insulators. Most of them come from the peculiar surface or edge states. Especially, the quantized anomalous Hall effect (QAHE) without an external magnetic field is realized in the two-dimensional ferromagnet on a three-dimensional TI which supports the dissipationless edge current. Here we demonstrate theoretically that the domain wall of this ferromagnet, which carries edge current, is charged and can be controlled by the external electric field. The chirality and relative stability of the Neel wall and Bloch wall depend on the position of the Fermi energy as well as the form of the coupling between the magnetic moments and orbital of the host TI. These findings will pave a path to utilize the magnets on TI for the spintronics applications.

No MeSH data available.


Related in: MedlinePlus

(a) Illustration of the domain wall in the ferromagnet on a TI. Along the domain wall, the gapless chiral edge channel appears (white stripe region). The angle ϕ specifies the type of the domain wall, i.e., ϕ = 0, π corresponds to Neel wall while ϕ = π/2, 3π/2 to Bloch wall. (b) The surface band structure with homogeneous ferromagnetic calculated from the 3D tight-binding model. The vertical axis is the energy in unit of t.
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f1: (a) Illustration of the domain wall in the ferromagnet on a TI. Along the domain wall, the gapless chiral edge channel appears (white stripe region). The angle ϕ specifies the type of the domain wall, i.e., ϕ = 0, π corresponds to Neel wall while ϕ = π/2, 3π/2 to Bloch wall. (b) The surface band structure with homogeneous ferromagnetic calculated from the 3D tight-binding model. The vertical axis is the energy in unit of t.

Mentions: In this paper, we investigate the stability and charging effects of a domain wall on the surface of the 3D TI based on the 3D tight-binding model. We carry out a numerical study based on the 3D tight-binding model293031. We also perform an analytical study based on the effective 2D surface Hamiltonian which we derive from the 3D model. The exchange coupling is found to be anisotropic due to the orbital dependence, as we have mentioned. Figure 1 shows the schematic structure of the domain wall on a TI. The angle ϕ determines the structure of the domain wall, i.e., Neel or Bloch wall and its chirality. It is found that the most stable domain wall structure depends on the position of the Fermi energy, i.e., one can control the domain structure by gating. Another important result is that the domain wall is charged due to the two effects: One originates in the zero-energy edge state along the domain wall and the other in the charging effect of the magnetic texture. It will offer a way to manipulate the domain wall by electric field.


Domain wall of a ferromagnet on a three-dimensional topological insulator.

Wakatsuki R, Ezawa M, Nagaosa N - Sci Rep (2015)

(a) Illustration of the domain wall in the ferromagnet on a TI. Along the domain wall, the gapless chiral edge channel appears (white stripe region). The angle ϕ specifies the type of the domain wall, i.e., ϕ = 0, π corresponds to Neel wall while ϕ = π/2, 3π/2 to Bloch wall. (b) The surface band structure with homogeneous ferromagnetic calculated from the 3D tight-binding model. The vertical axis is the energy in unit of t.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4555097&req=5

f1: (a) Illustration of the domain wall in the ferromagnet on a TI. Along the domain wall, the gapless chiral edge channel appears (white stripe region). The angle ϕ specifies the type of the domain wall, i.e., ϕ = 0, π corresponds to Neel wall while ϕ = π/2, 3π/2 to Bloch wall. (b) The surface band structure with homogeneous ferromagnetic calculated from the 3D tight-binding model. The vertical axis is the energy in unit of t.
Mentions: In this paper, we investigate the stability and charging effects of a domain wall on the surface of the 3D TI based on the 3D tight-binding model. We carry out a numerical study based on the 3D tight-binding model293031. We also perform an analytical study based on the effective 2D surface Hamiltonian which we derive from the 3D model. The exchange coupling is found to be anisotropic due to the orbital dependence, as we have mentioned. Figure 1 shows the schematic structure of the domain wall on a TI. The angle ϕ determines the structure of the domain wall, i.e., Neel or Bloch wall and its chirality. It is found that the most stable domain wall structure depends on the position of the Fermi energy, i.e., one can control the domain structure by gating. Another important result is that the domain wall is charged due to the two effects: One originates in the zero-energy edge state along the domain wall and the other in the charging effect of the magnetic texture. It will offer a way to manipulate the domain wall by electric field.

Bottom Line: Most of them come from the peculiar surface or edge states.Especially, the quantized anomalous Hall effect (QAHE) without an external magnetic field is realized in the two-dimensional ferromagnet on a three-dimensional TI which supports the dissipationless edge current.The chirality and relative stability of the Neel wall and Bloch wall depend on the position of the Fermi energy as well as the form of the coupling between the magnetic moments and orbital of the host TI.

View Article: PubMed Central - PubMed

Affiliation: Department of Applied Physics, University of Tokyo, 7-3-1, Hongo, Bunkyo-ku, Tokyo 113-8656, Japan.

ABSTRACT
Topological insulators (TIs) show rich phenomena and functions which can never be realized in ordinary insulators. Most of them come from the peculiar surface or edge states. Especially, the quantized anomalous Hall effect (QAHE) without an external magnetic field is realized in the two-dimensional ferromagnet on a three-dimensional TI which supports the dissipationless edge current. Here we demonstrate theoretically that the domain wall of this ferromagnet, which carries edge current, is charged and can be controlled by the external electric field. The chirality and relative stability of the Neel wall and Bloch wall depend on the position of the Fermi energy as well as the form of the coupling between the magnetic moments and orbital of the host TI. These findings will pave a path to utilize the magnets on TI for the spintronics applications.

No MeSH data available.


Related in: MedlinePlus