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Published on: March 24, 2019
Surface morphology of epitaxial magnetic tunnel junctions
M Mizuguchi1, Y Suzuki, T Nagahama
1Department of Materials Engineering Science, Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka 560-8531, Japan.
Epitaxial iron-magnesium oxide-iron magnetic tunnel junctions exhibit a giant tunneling magnetoresistance effect. Annealing creates flatter surfaces with steps and terraces, enhancing performance by eliminating pinholes in the magnesium oxide barrier.
Area of Science:
- Materials Science
- Condensed Matter Physics
- Nanotechnology
Background:
- Epitaxial magnetic tunnel junctions (MTJs) are crucial for spintronic devices.
- Giant tunneling magnetoresistance (TMR) effect in Fe/MgO/Fe structures is highly desirable.
- Controlling the interface and barrier quality is key to optimizing TMR.
Purpose of the Study:
- To investigate the surface morphology of epitaxial Fe(001)/MgO(001)/Fe(001) MTJs.
- To understand the impact of annealing on MgO barrier surface structure.
- To assess the integrity and electronic properties of MgO barrier layers.
Main Methods:
- In situ scanning tunneling microscopy (STM) for surface morphology analysis.
- In situ scanning tunneling spectroscopy (STS) for local electronic structure examination.
- Fabrication of epitaxial Fe/MgO/Fe(001) magnetic tunnel junctions.
Main Results:
- Epitaxial magnesium oxide (MgO) barrier layers form flat surface structures.
- Annealing results in a smoother MgO surface with distinct steps and terraces.
- Scanning tunneling spectroscopy revealed no pinholes in 1.05-nm-thick MgO barriers, indicating perfect barrier formation.
Conclusions:
- Optimized surface morphology of MgO barriers through annealing can enhance the TMR ratio.
- The absence of pinholes confirms the suitability of MgO as a perfect barrier for high-performance MTJs.
- In situ STM and STS are effective techniques for characterizing MTJ interfaces and predicting device performance.
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