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Large and Tunable Electron-Depletion-Based Voltage-Controlled Magnetic Anisotropy in the CoFeB/MgO System via
Yu-Chia Chen1, Thomas Peterson2, Qi Jia1
1Department of Electrical and Computer Engineering, University of Minnesota, Minneapolis, Minnesota 55455, United States.
ACS Nano
|April 14, 2025
Summary
Researchers enhanced the Voltage-Controlled Magnetic Anisotropy (VCMA) effect in Magnetic Random-Access Memory (MRAM) using W-Pt alloy underlayers. This approach significantly boosts VCMA efficiency, crucial for low-power embedded applications.
Area of Science:
- Materials Science
- Condensed Matter Physics
- Electrical Engineering
Background:
- Voltage-Controlled Magnetic Anisotropy (VCMA) is key for energy-efficient Magnetic Random-Access Memory (MRAM).
- Low VCMA efficiency in CoFeB/MgO interfaces limits MRAM performance.
- Experimental validation of predicted electron depletion (ED) effects on VCMA is needed.
Purpose of the Study:
- To enhance VCMA efficiency in CoFeB/MgO based MRAM.
- To investigate the impact of W-based alloy underlayers with varying Pt concentrations on VCMA.
- To experimentally confirm electron depletion at the CoFeB/MgO interface.
Main Methods:
- Synthesis of W-based metallic alloy underlayers with controlled Pt concentrations.
- Fabrication of MRAM devices utilizing these underlayers.
- Characterization using High-Resolution X-ray Photoelectron Spectroscopy (HR-XPS) to analyze interfacial electronic states.
Main Results:
- An approximately eightfold increase in VCMA coefficient was achieved with the optimal W-Pt alloy underlayer.
- Electrical-field tunable interfacial perpendicular magnetic anisotropy (PMA) was demonstrated.
- HR-XPS confirmed significant electron depletion in Fe orbitals at the CoFeB/MgO interface, evidenced by binding energy shifts.
Conclusions:
- W-Pt alloy underlayers provide an effective, industry-compatible method to enhance VCMA in MRAM.
- Controlling Fermi surface characteristics at the CoFeB/MgO interface under thermal equilibrium is crucial for improving VCMA efficiency.
- This work offers a pathway towards next-generation low-power MRAM devices.
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