Flexible magneto-ionic cells enabled by proton-driven magnetic modulation of transition metal oxides

Electric-field-driven ion motion is a rapidly evolving and powerful, energy-efficient approach to control magnetism, with broad implications in spintronics, nanomagnetism and related technological fields, including brain-inspired computing. Despite extensive research, most existing studies rely on either liquid electrolytes or solid-state configurations with rigid supports.

The Thesis Project aims at exploiting flexible magneto-ionic systems based on transition metal oxides (e.g., Ni–Co oxide solid solutions) and polymeric membranes (e.g., proton exchange membrane fuel cell) as ion-conducting medium. The fundamental idea is that by applying voltage, we drive protons into or out of the initially antiferromagnetic or paramagnetic metal oxide film, thereby enabling its reversible reduction to the metallic (ferromagnetic) phase and reoxidation back to the oxide phase. Notably, proton-based magneto-ionics is typically faster than other ion-based systems (like Li⁺, Na⁺, or O²⁻).

Depending on the nature of the initial metal oxide (antiferromagnetic or paramagnetic), degree of reduction, and interplay with the surrounding matrix, changes in saturation magnetization, coercivity or exchange bias are expected. This novel method would allow for solid-state electrochemical control of magnetism at significantly lower voltages compared to conventional capacitive systems. Different membranes (e.g., perfluorosulfonic acid, sulfonated poly(ether ether ketone) or sulfonated polyimides) will be tested. The transition metal oxides will be grown by sputtering. The device architecture, comprising the metal oxide film sandwiched between outer Pt thin films (all sputtered) and integrated with the polymeric membrane, will be subjected to repeated mechanical bending to assess its endurance. Electrostatics / potential distribution across Pt/membrane/oxide stack under applied voltage will be simulated to identify voltage drops (how much reaches the oxide). Ion (proton) transport and concentration profiles in the membrane and into the oxide (transient and steady state) will be simulated as well. The results obtained will be of potential interest for the implementation of new brain-inspired memory and computing concepts.

The candidate should have a solid background in materials science, physical chemistry, or related disciplines. Practical experience or keen interest in sputtering, electrochemistry, magnetic properties of materials, and standard materials characterization techniques (such as scanning electron microscopy, X-ray diffraction and magnetometry), and modelling will be considered an asset.

The candidate should be curious, adaptable, and collaborative, with strong problem-solving skills, as the project involves designing and testing device architectures beyond the state of the art.

Proficiency in data analysis and interpretation, the ability to deduce the underlying mechanisms of observed phenomena, and skill in disseminating findings through publications and presentations are all equally important.

The Gnm³ group (E. Pellicer, J. Sort) research focuses on the design, synthesis, and characterization of advanced materials with tailored properties for cutting-edge engineering applications. By precisely controlling their structure at the nanoscale, we create materials with superior mechanical strength, optimized magnetic performance, and enhanced thermal stability. We study a variety of systems, including nanowires, lithographically patterned micro- and nano-objects, mesoporous architectures, electrodeposited thin films, and nanocomposite/glassy alloys. Each offers opportunities to uncover new physical phenomena and functionalities.

Sustainability and energy efficiency are guiding principles of our work, shaping both the development of materials and their envisioned applications. In recent years, we have devoted particular attention to nanomaterials for brain-inspired memory and computing, with the aim of realizing energy-efficient, high-performance devices that bridge materials science and neuromorphic engineering.

The Transport Phenomena group (F. X. Àlvarez) has extensive experience in modelling transport processes from a multiscale perspective. They combine finite element modelling with ab initio simulations to determine transport parameters. By integrating these skills with the fabrication capabilities at Gnm3, they can strengthen research strategies aimed at discovering materials with enhanced properties.