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Ultrafast optical excitation of magnetic skyrmions

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ABSTRACT

Magnetic skyrmions in an insulating chiral magnet Cu2OSeO3 were studied by all-optical spin wave spectroscopy. The spins in the conical and skyrmion phases were excited by the impulsive magnetic field from the inverse-Faraday effect, and resultant spin dynamics were detected by using time-resolved magneto-optics. Clear dispersions of the helimagnon were observed, which is accompanied by a distinct transition into the skyrmion phase, by sweeping temperature and magnetic field. In addition to the collective excitations of skyrmions, i.e., rotation and breathing modes, several spin precession modes were identified, which would be specific to optical excitation. The ultrafast, nonthermal, and local excitation of the spin systems by photons would lead to the efficient manipulation of nano-magnetic structures.

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Spin dynamics as a function of external magnetic field.Spin precession frequencies and decay constants as a function of the external magnetic field, for (a),(b)  and (c) Hex∥[110].
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f5: Spin dynamics as a function of external magnetic field.Spin precession frequencies and decay constants as a function of the external magnetic field, for (a),(b) and (c) Hex∥[110].

Mentions: To scrutinize the observed spin modes, we plot the magnetic-field dependence of the spin precessions in Fig. 5 for the different magnetic-field orientations. For the Hex [Fig. 5(a)], the precession frequency decreases with increasing the Hex in the conical spin phase24, whereas increases with increasing Hex in the SkX phase. For the Hex//[110] [Fig. 5(c)], the frequency decreases in the SkX phase. These observations are consistent with the expected behaviors of the conical spin phase, rotation modes and the breathing mode of the skyemions, respectively17. Therefore, in addtion to the reasoning from its absolute frequency, the higher-lying mode in the SkX phase can be assigned to the CW rotation. The reentrant behavior of the conical phase by increasing the Hex, after experiencing a pocket of the SkX phase at 56.5 K [Fig. 5(a)], also supports the identification of the SkX phase, since this pocket is well isolated from other spin phases. It is also expected that the damping increases in the SkX phase25, which is roughly captured in our data in Fig. 5(b). The long-lasting spin precession at low temperatures [Fig. 2(b)] indicate that the spin scattering is mainly from thermal agitations.


Ultrafast optical excitation of magnetic skyrmions
Spin dynamics as a function of external magnetic field.Spin precession frequencies and decay constants as a function of the external magnetic field, for (a),(b)  and (c) Hex∥[110].
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5384326&req=5

f5: Spin dynamics as a function of external magnetic field.Spin precession frequencies and decay constants as a function of the external magnetic field, for (a),(b) and (c) Hex∥[110].
Mentions: To scrutinize the observed spin modes, we plot the magnetic-field dependence of the spin precessions in Fig. 5 for the different magnetic-field orientations. For the Hex [Fig. 5(a)], the precession frequency decreases with increasing the Hex in the conical spin phase24, whereas increases with increasing Hex in the SkX phase. For the Hex//[110] [Fig. 5(c)], the frequency decreases in the SkX phase. These observations are consistent with the expected behaviors of the conical spin phase, rotation modes and the breathing mode of the skyemions, respectively17. Therefore, in addtion to the reasoning from its absolute frequency, the higher-lying mode in the SkX phase can be assigned to the CW rotation. The reentrant behavior of the conical phase by increasing the Hex, after experiencing a pocket of the SkX phase at 56.5 K [Fig. 5(a)], also supports the identification of the SkX phase, since this pocket is well isolated from other spin phases. It is also expected that the damping increases in the SkX phase25, which is roughly captured in our data in Fig. 5(b). The long-lasting spin precession at low temperatures [Fig. 2(b)] indicate that the spin scattering is mainly from thermal agitations.

View Article: PubMed Central - PubMed

ABSTRACT

Magnetic skyrmions in an insulating chiral magnet Cu2OSeO3 were studied by all-optical spin wave spectroscopy. The spins in the conical and skyrmion phases were excited by the impulsive magnetic field from the inverse-Faraday effect, and resultant spin dynamics were detected by using time-resolved magneto-optics. Clear dispersions of the helimagnon were observed, which is accompanied by a distinct transition into the skyrmion phase, by sweeping temperature and magnetic field. In addition to the collective excitations of skyrmions, i.e., rotation and breathing modes, several spin precession modes were identified, which would be specific to optical excitation. The ultrafast, nonthermal, and local excitation of the spin systems by photons would lead to the efficient manipulation of nano-magnetic structures.

No MeSH data available.


Related in: MedlinePlus