Reversible and Irreversible Effects of Magneto-Ionic Gating: Exchange, Anisotropy, and Magnetization
Access to data, and its storage, is annually becoming of greater concern to consumers, companies, and governments. As the volume and generation of data grow, the technology that writes, reads, and secures it must become faster, more compact, and more efficient. Creating energy-efficient data storage...
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| Format: | Thesis |
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Massachusetts Institute of Technology
2024
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| Online Access: | https://hdl.handle.net/1721.1/155319 https://orcid.org/0000-0001-9233-1445 |
| Summary: | Access to data, and its storage, is annually becoming of greater concern to consumers, companies, and governments. As the volume and generation of data grow, the technology that writes, reads, and secures it must become faster, more compact, and more efficient. Creating energy-efficient data storage and logic devices has therefore become an urgent research focus. Magnetic storage, through voltage-controlled magnetism (VCM), uses orders of magnitude less energy than traditional current-controlled static and dynamic randomaccess memory. Herein, VCM is explored through the lens of magneto-ionics – a low-power, reversible, and non-volatile approach to the electric field control of magnetism. This thesis advances the understanding and optimization of magneto-ionic systems, focusing on the reversible and irreversible intricacies of the voltage-control of magnetic properties. In the initial exploration of Pd/Co/Pd trilayers via solid-state hydrogen-ion gating, the mechanism which toggles magnetic anisotropy is proven and quantitative values for the magneto-ionic modulation of magnetization and effective anisotropy are provided. The simple heterostructure also demonstrates the modulation of novel magnetic properties including spin angular momentum, orbital angular momentum, and proximity-induced moments. This understanding provides the foundation for a systematic optimization of Co/Pd multilayer heterostructures which achieves the highest reversible solid-state efficiency to date. Guided by this understanding, magneto-ionic gating is harnessed for modulation of the RKKY interlayer exchange interaction. This small applied bias voltage enables fully reversible, sub-millisecond, 180° voltage-controlled switching of the magnetic order. Moreover, by engineering the magnetic properties of the heterostructure, it enables field-free switching, a highly sought-after device property for magnetic memory. These findings not only contribute to the fundamental understanding of magneto-ionic phenomena, but also hold promise for the development of next-generation spintronic devices and non von Neumann computing architectures. By disentangling the complexities of the magneto-ionic manipulation of the exchange, anisotropy, and magnetization of magnetic materials, this thesis paves the way for enhanced functionality and performance in spin-based technologies, offering promising avenues for future research. |
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