In an information-driven world, the ability to securely process and store data has become crucial for nearly all sectors of human activity. As the quantity of generated data continues to grow rapidly, so does the energy required to handle and store it. Magnetic storage media continue to be widely used thanks to their high-density storage capacities and nonvolatility. However, further downscaling of devices to achieve higher bit densities causes substantial power losses due to Joule heating, which is also detrimental to the stability of the stored information. Addressing these challenges requires a paradigm shift in the design of hardware for future magnetic storage technologies. In addition to energy efficiency, novel forms of information processing, such as brain-inspired computing, require functionalities not inherent to conventional memory and logic technologies. Examples include logic-in-memory capabilities, nonlinearity, plasticity, analog tunability and stochasticity. Modulating magnetic properties with voltage is a promising avenue for the creation of ultralow power technologies for data storage and unconventional computing. This thesis explores the voltage control of magnetic phenomena in metallic thin film multilayers using ions. This approach, known as magnetoionics, has generated interest thanks to its ability to induce large magnetic effects with low voltages. This thesis investigates the intersection of two fields: voltage control of magnetism and Li-ion energy storage. Here, solid-state Li-ion batteries and supercapacitors are integrated with magnetic thin films to control their properties ionically. Three magnetic systems are considered: firstly, voltage switching of the magnetization of a Co/Pt bilayer between perpendicular and in-plane states is demonstrated in a Li-ion battery-like magnetoionic structure. Next, using a Li-ion supercapacitor, control of magnetic skyrmion nucleation and annihilation dynamics in a Pt/CoFeB/Pt system is achieved via Li-ion accumulation and depletion at the magnetic interface. Lastly, the reversible modulation of the strength and phase of the Ruderman-Kittel-Kasuya-Yosida (RKKY) interlayer interaction is realized in a perpendicularly magnetized [Co/Pt]N/Ru wedge/Pt/Co/Pt multilayer using a battery-like structure. The magnetoionic devices combine room temperature operation, high magnetoelectric coupling efficiencies, good endurance, short-term state retention, and fast response times to small voltages. The results of this work demonstrate an approach for the design of Li ion-based magnetoionic devices with functionalities suitable for novel computing applications.
|Translated title of the contribution||Solid-state lithium magnetoionics for voltage control of magnetic phenomena|
|Publication status||Published - 2023|
|MoE publication type||G5 Doctoral dissertation (article)|
- voltage control of magnetism
- perpendicular magnetization
- RKKY coupling
- solid-state lithium ion technologies