8 Microwave-Driven Dynamics of Magnetic Skyrmions …
193
-0.01
0
0.01
0.02
0.03
0.04
v
y (m/s)
0.03
0.06
0.09
0.12
-0.01
0
0.01
H ||x
H ||z
H ||y
(a)
(b)
R =0.0494 0.0666
0.0872
Rotation
(CounterCW) Breathing
H ex
x
y
z
H ||x
30°
H
H x
y y
H
H
| | y
H ||z
Rotation
(Clockwise)
v
x (m/s)
Fig. 8.5 Calculated microwave frequency dependence of the velocity v = (v x , v y ) for translational
motion of the skyrmion crystal induced by a microwave field H ω under a tilted H ext field H ex =
(H z tan θ, 0, H z ) with H z = 0.036 and θ = 30 ◦ . The system is irradiated by a microwave field
H ω
μ sin ωt (μ = x, y, z) with H ω
α = 0.0006 where ω = 2π f is its angular frequency. The velocities
show peaks at the resonant frequencies of the spin-wave modes, while their signs vary depending
on the mode and the microwave polarization (Reproduced from [29].)
microwave field H
ω
x activates the counterclockwise rotation mode. It is also
found that the speed and the direction of this translational motion sensitively depend
on the excited spin-wave mode and the microwave polarization.
8.5 Microwave-Electric-Field-Driven Translational Motion
of Isolated Skyrmions
In this section, we discuss an efficient method to drive isolated magnetic skyrmions
embedded in ferromagnetic environment with microwave electric fields instead of
microwave magnetic fields [30]. As mentioned in the introduction section, the magnetic skyrmions appear not only as a crystallized form but also as isolated defects
in the ferromagnetic phase. Recently possible application of magnetic skyrmions to
high-performance memory devices are studied intensively. For the usage as information carriers in memory devices, isolated magnetic skyrmions rather than crystallized
ones are recognized to be convenient. However, when a microwave magnetic field
is applied to a device to activate the isolated skyrmion defects, it is unavoidable to
193
-0.01
0
0.01
0.02
0.03
0.04
v
y (m/s)
0.03
0.06
0.09
0.12
-0.01
0
0.01
H ||x
H ||z
H ||y
(a)
(b)
R =0.0494 0.0666
0.0872
Rotation
(CounterCW) Breathing
H ex
x
y
z
H ||x
30°
H
H x
y y
H
H
| | y
H ||z
Rotation
(Clockwise)
v
x (m/s)
Fig. 8.5 Calculated microwave frequency dependence of the velocity v = (v x , v y ) for translational
motion of the skyrmion crystal induced by a microwave field H ω under a tilted H ext field H ex =
(H z tan θ, 0, H z ) with H z = 0.036 and θ = 30 ◦ . The system is irradiated by a microwave field
H ω
μ sin ωt (μ = x, y, z) with H ω
α = 0.0006 where ω = 2π f is its angular frequency. The velocities
show peaks at the resonant frequencies of the spin-wave modes, while their signs vary depending
on the mode and the microwave polarization (Reproduced from [29].)
microwave field H
ω
x activates the counterclockwise rotation mode. It is also
found that the speed and the direction of this translational motion sensitively depend
on the excited spin-wave mode and the microwave polarization.
8.5 Microwave-Electric-Field-Driven Translational Motion
of Isolated Skyrmions
In this section, we discuss an efficient method to drive isolated magnetic skyrmions
embedded in ferromagnetic environment with microwave electric fields instead of
microwave magnetic fields [30]. As mentioned in the introduction section, the magnetic skyrmions appear not only as a crystallized form but also as isolated defects
in the ferromagnetic phase. Recently possible application of magnetic skyrmions to
high-performance memory devices are studied intensively. For the usage as information carriers in memory devices, isolated magnetic skyrmions rather than crystallized
ones are recognized to be convenient. However, when a microwave magnetic field
is applied to a device to activate the isolated skyrmion defects, it is unavoidable to