206,383 research outputs found
Thermal gradient driven domain wall dynamics
The issue of whether a thermal gradient acts like a magnetic field or an
electric current in the domain wall (DW) dynamics is investigated. Broadly
speaking, magnetization control knobs can be classified as energy-driving or
angular-momentum driving forces. DW propagation driven by a static magnetic
field is the best-known example of the former in which the DW speed is
proportional to the energy dissipation rate, and the current-driven DW motion
is an example of the latter. Here we show that DW propagation speed driven by a
thermal gradient can be fully explained as the angular momentum transfer
between thermally generated spin current and DW. We found DW-plane rotation
speed increases as DW width decreases. Both DW propagation speed along the wire
and DW-plane rotation speed around the wire decrease with the Gilbert damping.
These facts are consistent with the angular momentum transfer mechanism, but
are distinct from the energy dissipation mechanism. We further show that
magnonic spin-transfer torque (STT) generated by a thermal gradient has both
damping-like and field-like components. By analyzing DW propagation speed and
DW-plane rotation speed, the coefficient ( \b{eta}) of the field-like STT
arising from the non-adiabatic process, is obtained. It is found that \b{eta}
does not depend on the thermal gradient; increases with uniaxial anisotropy
K_(||) (thinner DW); and decreases with the damping, in agreement with the
physical picture that a larger damping or a thicker DW leads to a better
alignment between the spin-current polarization and the local magnetization, or
a better adiabaticity
A Fast DOA Estimation Algorithm Based on Polarization MUSIC
A fast DOA estimation algorithm developed from MUSIC, which also benefits from the processing of the signals' polarization information, is presented. Besides performance enhancement in precision and resolution, the proposed algorithm can be exerted on various forms of polarization sensitive arrays, without specific requirement on the array's pattern. Depending on the continuity property of the space spectrum, a huge amount of computation incurred in the calculation of 4-D space spectrum is averted. Performance and computation complexity analysis of the proposed algorithm is discussed and the simulation results are presented. Compared with conventional MUSIC, it is indicated that the proposed algorithm has considerable advantage in aspects of precision and resolution, with a low computation complexity proportional to a conventional 2-D MUSIC
Domain wall propagation due to the synchronization with circularly polarized microwaves
Finding a new control parameter for magnetic domain wall (DW) motion in
magnetic nanostructures is important in general and in particular for the
spintronics applications. Here, we show that a circularly polarized magnetic
field (CPMF) at GHz frequency (microwave) can efficiently drive a DW to
propagate along a magnetic nanowire. Two motion modes are identified: rigid-DW
propagation at low frequency and oscillatory propagation at high frequency.
Moreover, DW motion under a CPMF is equivalent to the DW motion under a uniform
spin current in the current perpendicular to the plane magnetic configuration
proposed recently by Khvalkovskiy et al. [Phys. Rev. Lett. 102, 067206 (2009)],
and the CPMF frequency plays the role of the current
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