Highly cyclable voltage control of magnetism in cobalt ferrite nanopillars for memory and neuromorphic applications

Tuning the properties of magnetic materials by voltage-driven ion migration (magneto-ionics) gives potential for energy-efficient, non-volatile magnetic memory and neuromorphic computing. Here, we report large changes in the magnetic moment at saturation (mS) and coercivity (HC), of 34% and 78%, respectively, in an array of CoFe2O4 (CFO) epitaxial nanopillar electrodes (∼50 nm diameter, ∼70 nm pitch, and 90 nm in height) with an applied voltage of −10 V in a liquid electrolyte cell. Furthermore, a magneto-ionic response faster than 3 s and endurance >2000 cycles are demonstrated. The response time is faster than for other magneto-ionic films of similar thickness, and cyclability is around two orders of magnitude higher than for other oxygen magneto-ionic systems. Using a range of characterization techniques, magnetic switching is shown to arise from the modulation of oxygen content in the CFO. Also, the highly cyclable, self-assembled nanopillar structures were demonstrated to emulate various synaptic behaviors, exhibiting non-volatile, multilevel magnetic states for analog computing and high-density storage. Overall, CFO nanopillar arrays offer the potential to be used as interconnected synapses for advanced neuromorphic computing applications

Wear resistance of electrodeposited Fe-W alloy coatings under dry conditions and in the presence of rapeseed oil

Amorphous Fe-W alloys with 25 at.% of W were electrodeposited under direct and pulse modes from glycolate-citrate bath with and without addition of polyethylene glycol. The tribological behavior of the coatings was studied at 1, 2 and 5 N loads under dry friction and in the presence of rapeseed oil films of 0.2-5.0 m thickness. The tribological behavior of obtained coatings at dry friction reveals their severe tribo-oxidation resulting in a high wear depth and coefficient of friction. Observed groove like surface with well-adhered particles inside the wear track point out on abrasive-adhesive wear mechanism of Fe-W alloys. In the presence of rapeseed oil films the wear mechanism changes, and values of coefficient of friction decrease up to 10 times compared to dry friction conditions. The optimum thickness of rapeseed oil film was 1 µm. This film has the satisfactory adhesion and uniform distribution on the surface, and could withstand up to 2 000 cycles

Voltage-Induced ON Switching of Magnetism in Ordered Arrays of Non-Ferrimagnetic Nanoporous Iron Oxide Microdisks

Tailoring the magnetic properties of ordered arrays of patterned structures usually requires stringent control of their size, pitch, microstructure, and composition. Here, a fundamentally different approach to manipulate the magnetic behavior of lithographed microdisks, based on the application of electrical voltage, is demonstrated. First, highly porous iron oxide films with virtually no magnetic response (OFF state) are grown by sol\u2013gel chemistry. Subsequently, arrays of microdisks (8 \ub5m in diameter) are obtained combining lithography with wet chemical etching processes. Electrolyte-gating (with an anhydrous electrolyte) is then employed to induce a tunable (i.e., \u201con-demand\u201d) ferromagnetic response in these disks (OFF\u2013ON switching of magnetism) at room temperature. The changes in magnetic properties are attributed to magnetoelectrically-driven oxygen ion migration, which is enhanced due to nanoporosity. This causes partial reduction of the oxide phases to metallic Fe. The effect can be considerably reversed by applying voltage of opposite polarity. These results are appealing for diverse technological applications that require the use of patterned structures with easily tunable magnetic properties, such as magnetic micro-electro-mechanical systems, microfluidic, and lab-on-a-chip platforms for biomedical therapies and, ultimately, energy-efficient magnetic memories or neuromorphic computing

Tribological and corrosion properties of iron-based alloys

Corrosion is responsible for industrial maintenance and industrial accidents costs. A helpful way to prevent corrosion is to develop advanced materials with highly anti-corrosive properties. The electrodeposition is one of the most attractive methods for obtaining these materials. This work deals with evaluation of the tribological and corrosion behaviour of electrodeposited Fe-W and Fe-W-P alloys. Electrodeposits were obtained from 4 different baths and were characterized by means of scanning electron microscopy; X-ray dispersive energy spectroscopy; X-ray diffraction spectroscopy. The hardness was determined by Micro-indentation carried out at normal forces varying from 98 mN up to 980 mN with a loading rate of 1961 mN/min. A ball-disc tribometer was used to study the tribological properties at 90 °C. A diamond indenter, having a radius of 100 µm, was used to carry the scratch test. Corrosion behaviour was studied using polarization and electrochemical impedance spectroscopy technique. It was investigated that in all cases Fe-W and Fe-W-P alloy coatings exhibit greater micro-hardness than the stainless steel substrate. The amorphous-like ternary Fe-W-P alloy coatings demonstrate higher wear and corrosion resistance and lower friction coefficient compared to binary Fe-W alloy coatingVytauto Didžiojo universitetasŽemės ūkio akademij

Highly cyclable voltage control of magnetism in cobalt ferrite nanopillars for memory and neuromorphic applications

Tuning the properties of magnetic materials by voltage-driven ion migration (magneto-ionics) gives potential for energy-efficient, non-volatile magnetic memory and neuromorphic computing. Here, we report large changes in the magnetic moment at saturation (mS) and coercivity (HC), of 34% and 78%, respectively, in an array of CoFe2O4 (CFO) epitaxial nanopillar electrodes (∼50 nm diameter, ∼70 nm pitch, and 90 nm in height) with an applied voltage of −10 V in a liquid electrolyte cell. Furthermore, a magneto-ionic response faster than 3 s and endurance >2000 cycles are demonstrated. The response time is faster than for other magneto-ionic films of similar thickness, and cyclability is around two orders of magnitude higher than for other oxygen magneto-ionic systems. Using a range of characterization techniques, magnetic switching is shown to arise from the modulation of oxygen content in the CFO. Also, the highly cyclable, self-assembled nanopillar structures were demonstrated to emulate various synaptic behaviors, exhibiting non-volatile, multilevel magnetic states for analog computing and high-density storage. Overall, CFO nanopillar arrays offer the potential to be used as interconnected synapses for advanced neuromorphic computing applications.This work has received funding from the European Union’s Horizon 2020 research and innovation programme BeMAGIC under the Marie Sklodowska-Curie grant agreement No 861145. JLM-D and TM acknowledge support from the Royal Academy of Engineering Chair in Emerging Technologies Grant CiET1819\24, and the European Research Council ERC Advanced (grant agreement EU-H2020-ERC-ADG #882929), EROS. S.L. and J.L.M.-D. thank Trinity College at Cambridge for partial support. Partial financial support from the Spanish Government (PID2020-116844RB-C21, PDC2021-121276-C31, PID2020 116844RB-C22, and PDC2021-121276-C32), and the Generalitat de Catalunya (2021-SGR 00651) is also acknowledged. A.N acknowledges funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement Nº 892661– MAGNUS. BZ. We are grateful to the UK Materials and Molecular Modelling Hub for computational resources, which is partially funded by EPSRC (EP/P020194/1 and EP/T022213/1)