Magneto‐Ionic Switching of Superparamagnetism

Abstract

Electrochemical reactions represent a promising approach to control magnetization via electric fields. Favorable reaction kinetics have made nanoporous materials particularly interesting for magnetic tuning experiments. A fully reversible ON and OFF switching of magnetism in nanoporous Pd(Co) at room temperature is demonstrated, triggered by electrochemical hydrogen sorption. Comprehensive magnetic characterization in combination with high-resolution scanning transmission electron microscopy reveals the presence of Co-rich, nanometer-sized clusters in the nanoporous Pd matrix with distinct superparamagnetic behavior. The strong magneto-ionic effect arises from coupling of the magnetic clusters via a Ruderman-Kittel-Kasuya-Yoshida-type interaction in the Pd matrix which is strengthened upon hydrogen sorption. This approach offers a new pathway for the voltage control of magnetism, for application in spintronic or microelectromagnetic devices.We demonstrate a highly reproducible room temperature switching between magnetic states in npPd(Co) which enables full voltage control of magnetism.

Roadmap on Magnetoelectric Materials and Devices

“…Hydrogen atoms can diffuse via interstitial sites at high mobility rates (due to their small size), rendering hydrogen-mediated magneto-ionics a very promising approach to circumvent the limited operation speed and cyclability of oxygen magneto-ionics. Hydrogen magneto-ionics have been demonstrated both in solid and liquid [320,335,336,[353][354][355][356][357][358][359] electrolyte configurations. In solid state, Tan et al [336] showed a voltage-induced spin reorientation in Au/GdOx/Co(0.9 nm)/Pt stacks assisted by humid environment, with endurance of up to 2000 cycles, wherein hydrogen accumulation at the GdOx/Co interface caused a modification of the interface magnetic anisotropy.…”

“…Using liquid aqueous electrolyte configuration, Maroun et al demonstrated a reversible increase and decrease of perpendicular coercivity in Pd/Co/Au multilayer stacks arising from hydrogenation of the Pd layer [353]. A transition from superparamagnetic to ferromagnetic behavior [20] was demonstrated in nanoporous Pd(Co) assisted by a Ruderman-Kittel-Kasuya-Yosida-type interaction in the Pd matrix, also due to electrochemical H + reduction to H and subsequent H absorption in this material [357]. Hydrogenbased magneto-ionics was also shown in SrCoO3- [358] and NiCo2O4 films [359].…”

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

“…[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.…”

Voltage-driven motion of nitrogen ions: a new paradigm for magneto-ionics

“…agneto-ionics [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17] , i.e., the change in the magnetic properties of materials due to electric field-induced ion motion, is acquiring a leading role, among other magnetoelectric mechanisms (intrinsic 18 or extrinsic 19 multiferroicity, electric charge accumulation [20][21][22], to control magnetism with voltage 23,24 . This is triggered by its capability to largely modulate magnetic properties in a permanent and energy-efficient way 2,25 .…”