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Nonlinear giant magnetoresistance in dual spin valves
1Department of Materials Science, Cambridge University, Pembroke Street, Cambridge CB2 3QZ, United Kingdom.
Physical Review Letters
|April 7, 2010
Summary
Giant magnetoresistance (GMR) in metallic heterostructures exhibits nonlinear behavior due to current-dependent scattering. This phenomenon arises from highly nonequilibrium spin accumulation, challenging current GMR understanding.
Area of Science:
- Condensed Matter Physics
- Materials Science
- Spintronics
Background:
- Giant magnetoresistance (GMR) is a quantum mechanical effect observed in multilayer structures.
- GMR arises from spin-dependent scattering of electrons in ferromagnetic (FM) and nonmagnetic layers.
- Current GMR understanding assumes spin-independent scattering asymmetries.
Purpose of the Study:
- To investigate the nonlinear behavior of GMR in metallic heterostructures.
- To explore the role of nonequilibrium spin accumulation in GMR.
- To challenge and extend the current understanding of GMR.
Main Methods:
- Fabrication of metallic heterostructures with ferromagnetic and nonmagnetic layers.
- Electrical transport measurements to characterize GMR.
- Analysis of current-dependent resistance and spin accumulation.
Main Results:
- Observed a current-dependent nonlinear GMR.
- Demonstrated that highly nonequilibrium spin accumulation drives this nonlinearity.
- Showed that current-dependent scattering asymmetries in ultrathin FM layers explain the behavior.
Conclusions:
- The study reveals a novel nonlinear GMR phenomenon not predicted by current theories.
- Nonequilibrium spin accumulation and current-dependent scattering are key to understanding this GMR behavior.
- Findings necessitate an update to the theoretical framework of GMR.
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