2 research outputs found
Enhancing Magneto Ionic Effects in Magnetic Nanostructured Films via Conformal Deposition of Nanolayers with Oxygen Acceptor Donor Capabilities
Effective manipulation of the magnetic properties of nanostructured metallic alloys, exhibiting intergrain porosity (i.e., channels) and conformally coated with insulating oxide nanolayers, with an electric field is demonstrated. Nanostructured Co–Pt films are grown by electrodeposition (ED) and subsequently coated with either AlOx or HfOx by atomic layer deposition (ALD) to promote magneto-ionic effects (i.e., voltage-driven ion migration) during electrolyte gating. Pronounced variations in coercivity (HC) and magnetic moment at saturation (mS) are found at room temperature after biasing the heterostructures. The application of a negative voltage results in a decrease of HC and an increase of mS, whereas the opposite trend is achieved for positive voltages. Although magneto-ionic phenomena are already observed in uncoated Co–Pt films (because of the inherent presence of oxygen), the ALD oxide nanocoatings serve to drastically enhance the magneto-ionic effects because of partially reversible oxygen migration, driven by voltage, across the interface between AlOx or HfOx and the nanostructured Co–Pt film. Co–Pt/HfOx heterostructures exhibit the most significant magneto-electric response at negative voltages, with an increase of mS up to 76% and a decrease of HC by 58%. The combination of a nanostructured magnetic alloy and a skinlike insulating oxide nanocoating is shown to be appealing to enhance magneto-ionic effects, potentially enabling electrolyte-gated magneto-ionic technology.Financial support by the European Research Council (SPIN-PORICS 2014-Consolidator Grant, agreement no. 648454), the Spanish Government (Project MAT2017-86357-C3-1-R, MAT2017-83169-R “Severo Ochoa” Programme for Centres of Excellence in R&D SEV-2015-0496 and associated FEDER), the Generalitat de Catalunya (2017-SGR-292 and 2017-SGR-1519), and the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement no. 665919 is acknowledged. P.Y. acknowledges the Chinese Scholarship Council CSC fellowship (201606920073).Peer reviewe
Large Magnetoelectric Effects in Electrodeposited Nanoporous Microdisks Driven by Effective Surface Charging and Magneto Ionics
A synergetic
approach to enhance magnetoelectric effects (i.e.,
control of magnetism with voltage) and improve energy efficiency in
magnetically actuated devices is presented. The investigated material
consists of an ordered array of Co–Pt microdisks, in which
nanoporosity and partial oxidation are introduced during the synthetic
procedure to synergetically boost the effects of electric field. The
microdisks are grown by electrodeposition from an electrolyte containing
an amphiphilic polymeric surfactant. The bath formulation is designed
to favor the incorporation of oxygen in the form of cobalt oxide.
A pronounced reduction of coercivity (88%) and a remarkable increase
of Kerr signal amplitude (60%) are observed at room temperature upon
subjecting the microdisks to negative voltages through an electrical
double layer. These large voltage-induced changes in the magnetic
properties of the microdisks are due to (i) the high surface-area-to-volume
ratio with ultranarrow pore walls (sub-10 nm) that promote enhanced
electric charge accumulation and (ii) magneto-ionic effects, where
voltage-driven O<sup>2–</sup> migration promotes a partial
reduction of CoO to Co at room temperature. This simple and versatile
procedure to fabricate patterned “nano-in-micro” magnetic
motifs with adjustable voltage-driven magnetic properties is very
appealing for energy-efficient magnetic recording systems and other
magnetoelectronic devices