Research Update: Magnetoionic control of magnetization and anisotropy in layered oxide/metal heterostructures

Duschek, Kenny; Pohl, Darius; Fähler, S.; Nielsch, Kornelius; Leistner, K.

doi:10.1063/1.4942636

Cited by 30 publications

(39 citation statements)

References 46 publications

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“…Furthermore, the applied voltage was carefully chosen within a specific potential window in order to insert/remove the cations without disrupting the crystal structure of the electrode. A magnetization change of up to 64% and 86% was respectively attained in thin films [172] and nanoislands [173] of iron covered with 1 m KOH aqueous solution via quasi-reversible electrooxidation and electroreduction processes. Thereafter, following a similar approach, a larger variation of magnetization up to 50% and 70% was obtained in bulk CuFe 2 O 4 and ZnFe 2 O 4 powders, [44] respectively.…”

Section: Me Coupling Via Ionic Intercalationmentioning

confidence: 99%

Voltage‐Control of Magnetism in All‐Solid‐State and Solid/Liquid Magnetoelectric Composites

2019

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activities. [1][2][3][4][5][6][7][8][9][10][11][12] From a technological perspective, several low-power ME applications have been envisioned, comprising devices for memory storage and processing, [13,14] tuning and filtering of RF/microwave signals, [15,16] energy conversion and harvesting, [17,18] sensing, [19,20] and actuation. [21,22] By definition, the direct ME effect is manifested when an electric polarization P is induced by usage of a magnetic field H in accordance with Δ Δ to compare the strength of the interaction between electricity and magnetism among different magnetoelectric systems. chemical control of the physical (magnetic) properties in metals and oxide nanostructures; electrostatic doping via field-effect; reversible magnetic phase transitions induced with ionic liquid charging; spintronics; printed electronics; fabrication of solution-processed devices (transistors, etc.)There are some nontrivial reasons explaining why solid/ liquid ME composites developed later than all-solid-state approaches. From an experimental perspective, the usage of conventional aqueous electrolytes poses some restrictions in terms of the operating conditions. Concerning the applied voltage, water electrolysis already occurs at a low voltage of

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Section: Me Coupling Via Ionic Intercalationmentioning

confidence: 99%

Voltage‐Control of Magnetism in All‐Solid‐State and Solid/Liquid Magnetoelectric Composites

2019

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“…The observed change in ΔI is qualitatively con sistent with this, and also with previously observed changes in M S for FeO x /Fe films polarized in alkaline electrolytes. [16] The in plane angular distribution of coercivity and M R /M S ratio, respectively, were extracted from angleresolved Kerr measurements from 0° to 180° in steps of 10° for both pristine (black symbols and gray area) and reduced state (blue symbols and blue area) (Figure 4e,f). The dominant twofold symmetry reflects the mentioned uniaxial anisotropy.…”

Section: Reduction/oxidation Leads To Reversible Voltage-induced Collmentioning

confidence: 99%

“…[31][32][33][34] For such materials, voltageswitching between antiferromagnetic and ferromagnetic or ferrimagnetic states is demonstrated. [32,35] Further, studies on layered composites and nanoporous metal alloys indicate that also many other exciting magnetic phe nomena, such as the exchange bias, [14] spin reorientation, [16,36] and the RKKY interaction [37] length are tunable by electrolytic gating. Although films with uniaxial inplane anisotropy hold great potential for switchable artificial magnetic stray field landscapes for labonachip [38] or for giant magnetoresistance sensors, [39] there are no reports of magnetoionic control of such films yet.…”

Section: Introductionmentioning

confidence: 99%

Voltage‐Controlled Deblocking of Magnetization Reversal in Thin Films by Tunable Domain Wall Interactions and Pinning Sites

Zehner

Soldatov

Schneider

et al. 2020

Adv Elect Materials

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so far, mainly originates from the elec tric currents utilized to control the mag netic properties. A promising alternative for increasing the energy efficiency of magnetic devices is to control the mag netism by electric fields instead of electric currents. This possibility has triggered intense research into magnetoelectric materials, but much of this is restricted to low temperature and high voltage opera tion and/or complex layer synthesis. [1] More recently, magnetoelectric appro aches involving the voltagegating of mag netic nanostructures via a dielectric oxide or an electrolyte were examined. [1-3] In these approaches, ferro and ferrimagnetic metals or oxides exhibiting Curie tem peratures above room temperature can be used and often only few volts are required during gating. The modulation of mag netic properties in voltagegated magnetic nanostructures is based on either voltage induced capacitive charging or electro chemical (magnetoionic) processes. [2-4] Voltageinduced capacitive charging of a ferromagnetic metal interface causes volatile changes in the sur face electronic band structure that affect the intrinsic magnetic properties in just a few atomic layers. [5-10] In contrast, magneto ionic mechanisms involve voltageinduced ion migration and electrochemical reactions, [2,3,11-13] and can therefore induce very large and nonvolatile magnetic property changes. [12,14-18] As a High energy efficiency of magnetic devices is crucial for applications such as data storage, computation, and actuation. Redox-based (magneto-ionic) voltage control of magnetism is a promising room-temperature pathway to improve energy efficiency. However, for ferromagnetic metals, the magnetoionic effects studied so far require ultrathin films with tunable perpendicular magnetic anisotropy or nanoporous structures for appreciable effects. This paper reports a fully reversible, low voltage-induced collapse of coercivity and remanence by redox reactions in iron oxide/iron films with uniaxial in-plane anisotropy. In the initial iron oxide/iron films, Néel wall interactions stabilize a blocked state with high coercivity. During the voltage-triggered reduction of the iron oxide layer, in situ Kerr microscopy reveals inverse changes of coercivity and anisotropy, and a coarsening of the magnetic microstructure. These results confirm a magneto-ionic deblocking mechanism, which relies on changes of the Néel wall interactions, and of the microstructural domainwall-pinning sites. With this approach, voltage-controlled 180° magnetization switching with high energy-efficiency is achieved. It opens up possibilities for developing magnetic devices programmable by ultralow power and for the reversible tuning of defect-controlled materials in general.

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“…In the past few years electrolyte gating of magnetic materials has been established as a powerful method to manipulate magnetism . Electrolytes allow for reversible modulation of appreciably higher charge carrier densities (>10 14 cm −2 ) than high‐κ dielectrics and ferroelectrics using lower voltages.…”

mentioning

confidence: 99%

“…ME coupling has been realized at the interface of solid/liquid devices via surface electrostatic doping (as in electric double‐layer (EDL) capacitors) or via bulk ionic migration (akin to electrochemical batteries). Recently, robust ME effect was achieved in magnetic supercapacitors via a surface electrochemical mechanism called pseudocapacitance . By making use of interfacial redox reactions, pseudocapacitors concurrently benefit of fast, reversible charging/discharging processes (typical of EDL capacitors) and high amounts of stored charge (typical of electrochemical batteries).…”

mentioning

confidence: 99%

Voltage‐Controlled On/Off Switching of Ferromagnetism in Manganite Supercapacitors

2017

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liquid devices via surface electrostatic doping [20][21][22][23] (as in electric doublelayer (EDL) capacitors) or via bulk ionic migration [12,[15][16][17][18][19] (akin to electrochemical batteries). Recently, robust ME effect was achieved in magnetic supercapacitors [24,25] via a surface electrochemical mechanism called pseudocapacitance. [26,27] By making use of interfacial redox reactions, pseudocapacitors concurrently benefit of fast, reversible charging/discharging processes (typical of EDL capacitors) and high amounts of stored charge (typical of electrochemical batteries).From a technological perspective, the idea of controlling magnetic phase transitions in a supercapacitor where the magnetic counterpart is composed of a manganese-based oxide is very appealing. Indeed, several manganites [28] exhibit ferromagnetism and high degree of spin polarization intrinsically coupled to each other in proximity of room temperature. Thus, a low-power electric field could enable the simultaneous switching of magnetic and spintronic degrees of freedom without losing reversibility and switching speed.In this work, we selected, as a model system, a magnetic manganite supercapacitor made of an ultrathin film of La 0.74 Sr 0.26 MnO 3 (LSMO) charged with an ionic liquid electrolyte (DEME + -TFSI − ). By exploiting surface capacitive and pseudocapacitive charging mechanisms, we demonstrate the repetitive and complete suppression and recovery of ferromagnetism in LSMO at low-energy cost and remarkable switching speed in the 200-250 K temperature range.Atomically smooth LSMO films (see Figure 1a) with an optimized thickness of ≈3 nm and a surface area of ≈0.4 cm 2 were epitaxially grown on (001)-oriented SrTiO 3 (STO) substrates by magnetron sputtering. For a film thickness of ≈3 nm, a good compromise has been reached to maintain a high surfaceto-volume ratio and to preserve the Curie temperature of LSMO above the freezing point of the ionic liquid.In order to quantitatively track the LSMO magnetization while charging its surface with an ionic liquid, superconducting quantum interference device (SQUID) magnetometry and cyclic voltammetry (CV) measurements were combined and synchronized in situ (see the Experimental Section). The solid/ liquid devices consisted of a ME tuning cell with a configuration similar to an electrolytic capacitor (see sketch in Figure 1b).By application of a positive (negative) external voltage, the TFSI − (DEME + ) ions accumulate onto the surface of LSMO The ever-growing technological demand for more advanced microelectronic and spintronic devices keeps catalyzing the idea of controlling magnetism with an electric field. Although voltage-driven on/off switching of magnetization is already established in some magnetoelectric (ME) systems, often the coupling between magnetic and electric order parameters lacks an adequate reversibility, energy efficiency, working temperature, or switching speed. Here, the ME performance of a manganite supercapacitor composed of a ferromagnetic, spin-polarized ultrathin...

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Research Update: Magnetoionic control of magnetization and anisotropy in layered oxide/metal heterostructures

Cited by 30 publications

References 46 publications

Voltage‐Control of Magnetism in All‐Solid‐State and Solid/Liquid Magnetoelectric Composites

Voltage‐Control of Magnetism in All‐Solid‐State and Solid/Liquid Magnetoelectric Composites

Voltage‐Controlled Deblocking of Magnetization Reversal in Thin Films by Tunable Domain Wall Interactions and Pinning Sites

Voltage‐Controlled On/Off Switching of Ferromagnetism in Manganite Supercapacitors

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