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Relationship between nonadiabaticity and damping in permalloy studied by current induced spin structure
1Fachbereich Physik, Universität Konstanz, Universitätsstrasse 10, D-78457 Konstanz, Germany.
Physical Review Letters
|March 21, 2008
Summary
Spin transfer torque induces domain wall transformations in Permalloy, with vortex core motion perpendicular to current flow. Non-adiabaticity parameter beta is shown to differ from damping alpha.
Area of Science:
- Condensed matter physics
- Materials science
- Nanotechnology
Background:
- Spin transfer torque (STT) is a phenomenon where angular momentum is transferred from a spin-polarized current to magnetic materials.
- Understanding domain wall dynamics in magnetic nanostructures is crucial for developing advanced memory and logic devices.
Purpose of the Study:
- To investigate spin structure changes in Permalloy (Py) wires and disks induced by spin transfer torque.
- To determine critical current densities for different domain wall types and analyze vortex core motion.
Main Methods:
- Direct imaging techniques were employed to observe spin structure evolution.
- Spin transfer torque was applied to Permalloy wires and disks.
- Critical current densities were measured for various domain wall configurations.
Main Results:
- Periodic transformations between transverse and vortex domain walls were observed in Permalloy wires.
- Vortex core displacement perpendicular to the current direction was identified as the transformation mechanism.
- The non-adiabaticity parameter (beta) was found to be unequal to the damping parameter (alpha).
- Vortex core motion in disks showed directionality dependent on core polarity.
Conclusions:
- The observed domain wall transformations and vortex core dynamics provide insights into non-adiabatic spin transfer effects.
- Results support theoretical predictions that beta is not equal to alpha.
- Understanding vortex core polarity-dependent motion is key for spintronic device design.
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