研究目的
To study reversible domain wall motion in half-ring Ni80Fe20 nanowires on a nanosecond timescale using a current-induced pump-probe experiment and to observe lateral domain wall oscillations, comparing them to a string model.
研究成果
Reversible oscillations of a domain wall in a magnetic nanowire were excited by current pulses exerting spin-transfer torque, with the motion describable by a string model. The study demonstrates the feasibility of current-induced domain wall motion in pump-probe experiments, suggesting potential for future applications in spintronic devices, though further optimization and experimentation are needed.
研究不足
The motion cannot be exactly pinned down due to the limited number of experimental time stamps and uncertainties in parameters such as additional pinning, effective mass values from references, and the assumption of harmonic oscillation. The current pulse shape was not ideal, and technical constraints prevented perfect impedance matching.
1：Experimental Design and Method Selection:
A pump-probe setup was designed using an energy-filtered, aberration-corrected photoemission electron microscope (PEEM) with X-ray magnetic circular dichroism (XMCD) for magnetic imaging. Current pulses were injected directly into the nanowire to induce domain wall motion, and synchronization with synchrotron radiation pulses allowed for time-resolved measurements.
2：Sample Selection and Data Sources:
Ni80Fe20 half-ring shaped nanowires with an artificial pinning site (triangular notch) were fabricated on GaAs substrates using electron-beam lithography and a two-step lift-off process. Gold contact pads were added for current injection.
3：List of Experimental Equipment and Materials:
Equipment included an aberration-corrected PEEM, synchrotron radiation source, avalanche photo-diode (APD) for generating current pulses, diode-laser for triggering, and high-voltage power supplies. Materials included Ni80Fe20 nanowires, GaAs substrates, and gold for capping and contacts.
4：Experimental Procedures and Operational Workflow:
The magnetization was initialized with an in-plane magnetic field. Current pulses (~1 ns length) were generated by triggering an APD with a laser, synchronized to synchrotron x-ray pulses. XMCD images were recorded at various time delays to map the temporal evolution of domain wall motion.
5：Data Analysis Methods:
The domain wall oscillations were analyzed by comparing experimental images to a string model, calculating oscillation frequencies using known parameters for tension and effective mass.
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