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Terahertz Spin-Conductance Spectroscopy: Probing Coherent and Incoherent Ultrafast Spin Tunneling
Reza Rouzegar1,2, Mohamed Amine Wahada3,4, Alexander L Chekhov1,2
1Department of Physics, Freie Universität Berlin, 14195 Berlin, Germany.
Nano Letters
|June 21, 2024
Summary
We developed a terahertz spectroscopy method to measure spin conductance in spintronic devices. This technique reveals insights into ultrafast spin transport, particularly through MgO barriers, highlighting resonant tunneling dynamics.
Area of Science:
- Spintronics
- Condensed Matter Physics
- Materials Science
Background:
- Ferromagnetic/heavy-metal thin-film stacks are fundamental spintronic model systems.
- Understanding spin transport dynamics at high frequencies is crucial for spintronic device applications.
- Terahertz frequencies represent the natural timescale for spin-transport phenomena.
Purpose of the Study:
- To develop and apply a method for measuring ultrabroadband spin conductance at terahertz frequencies.
- To investigate spin transport across MgO tunneling barriers of varying thicknesses (0-6 Å).
- To elucidate the mechanisms governing spin conductance, including coherent and incoherent tunneling.
Main Methods:
- Development of a terahertz spectroscopy technique to probe spin conductance.
- Application of the method to thin-film stacks incorporating MgO tunneling barriers.
- Time-domain analysis of spin conductance (G_s) to identify distinct temporal components.
Main Results:
- Identified two components of spin conductance: an instantaneous feature and a longer-lived component.
- The longer-lived component, attributed to incoherent resonant spin tunneling via MgO defect states, shows a relaxation time that increases with barrier thickness (up to 270 fs at 6.0 Å).
- Experimental results are in excellent agreement with an analytical model.
Conclusions:
- Terahertz spin-conductance spectroscopy is a powerful tool for probing ultrafast spin transport.
- The study reveals the significant role of MgO defect states in mediating incoherent resonant spin tunneling.
- This technique offers new insights into spin dynamics in diverse spintronic nanostructures.
Keywords:
MgO tunnel junctionsTerahertz spintronicscoherent tunnelingincoherent resonant tunnelingspin conductanceterahertz spectroscopyMore Related Videos
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