Robustness of Voltage-induced Magnetocapacitance

Kaiju, Hideo; Misawa, Takahiro; Nagahama, Taro; Komine, Takashi; Kitakami, Osamu; Fujioka, M.; Nishii, Junji; Xiao, Gang

doi:10.1038/s41598-018-33065-y

Cited by 12 publications

(10 citation statements)

References 65 publications

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“…The V 1/2 of TMC is almost twice as high as that of TMR in MgO-based MTJs 31 . Our recent work also demonstrates that TMC actually slightly increases from 98% up to 102% upon biasing, which correspondingly causes the TMR to decay from 100% to 50% 32 .…”

Section: Introductionmentioning

confidence: 69%

“…As a complementary effect to TMR, tunneling magnetocapacitance (TMC) is now actively being investigated due to its unique properties, such as high magnetic sensitivity, thermal stability, and robustness against bias voltage 28 – 32 . Since the magnetocapacitance (MC) effect is observed in a system with broken time-reversal and space-inversion symmetry, the research of TMC is of particular importance for both practical applications and for fundamental physics 28 .…”

Section: Introductionmentioning

confidence: 99%

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Observation and theoretical calculations of voltage-induced large magnetocapacitance beyond 330% in MgO-based magnetic tunnel junctions

Ogata

Nakayama

Xiao

et al. 2021

Sci Rep

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Magnetic tunnel junctions (MTJs) in the field of spintronics have received enormous attention owing to their fascinating spin phenomena for fundamental physics and potential applications. MTJs exhibit a large tunnel magnetoresistance (TMR) at room temperature. However, TMR depends strongly on the bias voltage, which reduces the magnitude of TMR. On the other hand, tunnel magnetocapacitance (TMC), which has also been observed in MTJs, can be increased when subjecting to a biasing voltage, thus exhibiting one of the most interesting spin phenomena. Here we report a large voltage-induced TMC beyond 330% in MgO-based MTJs, which is the largest value ever reported for MTJs. The voltage dependence and frequency characteristics of TMC can be explained by the newly proposed Debye-Fröhlich model using Zhang-sigmoid theory, parabolic barrier approximation, and spin-dependent drift diffusion model. Moreover, we predict that the voltage-induced TMC ratio could reach over 3000% in MTJs. It is a reality now that MTJs can be used as capacitors that are small in size, broadly ranged in frequencies and controllable by a voltage. Our theoretical and experimental findings provide a deeper understanding on the exact mechanism of voltage-induced AC spin transports in spintronic devices. Our research may open new avenues to the development of spintronics applications, such as highly sensitive magnetic sensors, high performance non-volatile memories, multi-functional spin logic devices, voltage controlled electronic components, and energy storage devices.

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Section: Introductionmentioning

confidence: 69%

Section: Introductionmentioning

confidence: 99%

Observation and theoretical calculations of voltage-induced large magnetocapacitance beyond 330% in MgO-based magnetic tunnel junctions

Ogata

Nakayama

Xiao

et al. 2021

Sci Rep

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“…Magnetic tunnel junctions (MTJs) 4 , 8 , 19 are a common spintronic device and can exhibit a large MC effect at room temperature, often referred to as tunnel magnetocapacitance (TMC) 2 – 4 , 7 – 9 . MTJs are also known to show a large tunnel magnetoresistance (TMR) effect 20 – 26 .…”

Section: Introductionmentioning

confidence: 99%

“…MTJs are also known to show a large tunnel magnetoresistance (TMR) effect 20 – 26 . TMC’s unique properties include a relative larger TMC (measured in percentage) over TMR at some specific frequencies 4 , good thermal stability in TMC 19 , and robustness of TMC against a bias voltage as opposed to a bias-induced TMR drop 8 . Recently, by optimizing appropriate frequencies and bias voltages, a large TMC of 332% was achieved in MgO-based MTJs at room temperature 27 .…”

Section: Introductionmentioning

confidence: 99%

Large magnetocapacitance beyond 420% in epitaxial magnetic tunnel junctions with an MgAl2O4 barrier

Sato

Sukegawa

Ogata

et al. 2022

Sci Rep

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Magnetocapacitance (MC) effect has been observed in systems where both symmetries of time-reversal and space-inversion are broken, for examples, in multiferroic materials and spintronic devices. The effect has received increasing attention due to its interesting physics and the prospect of applications. Recently, a large tunnel magnetocapacitance (TMC) of 332% at room temperature was reported using MgO-based (001)-textured magnetic tunnel junctions (MTJs). Here, we report further enhancement in TMC beyond 420% at room temperature using epitaxial MTJs with an MgAl2O4(001) barrier with a cation-disordered spinel structure. This large TMC is partially caused by the high effective tunneling spin polarization, resulted from the excellent lattice matching between the Fe electrodes and the MgAl2O4 barrier. The epitaxial nature of this MTJ system sports an enhanced spin-dependent coherent tunneling effect. Among other factors leading to the large TMC are the appearance of the spin capacitance, the large barrier height, and the suppression of spin flipping through the MgAl2O4 barrier. We explain the observed TMC by the Debye-Fröhlich modelled calculation incorporating Zhang-sigmoid formula, parabolic barrier approximation, and spin-dependent drift diffusion model. Furthermore, we predict a 1000% TMC in MTJs with a spin polarization of 0.8. These experimental and theoretical findings provide a deeper understanding on the intrinsic mechanism of the TMC effect. New applications based on large TMC may become possible in spintronics, such as multi-value memories, spin logic devices, magnetic sensors, and neuromorphic computing.

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“…TMR sensors are based on a promising technology in spintronic research, in which conventional electronics make use of charge carrier mobility for either information or power transfer [35], [36]. Spintronics uses an extra degree of freedom from electrons, commonly referred to as 'spin', where electrons intrinsically spin upon their axis in either a clockwise (spin-up) or anti-clockwise (spin down) direction [37].…”

Section: Introductionmentioning

confidence: 99%

Spintronic Sensors Based on Magnetic Tunnel Junctions for Wireless Eye Movement Gesture Control

Tanwear

Liang

Liu

et al. 2020

IEEE Trans. Biomed. Circuits Syst.

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The tracking of eye gesture movements using wearable technologies can undoubtedly improve quality of life for people with mobility and physical impairments by using spintronic sensors based on the tunnel magnetoresistance (TMR) effect in a human-machine interface. Our design involves integrating three TMR sensors on an eyeglass frame for detecting relative movement between the sensor and tiny magnets embedded in an in-house fabricated contact lens. Using TMR sensors with the sensitivity of 11mV/V/Oe and ten <1 mm 3 embedded magnets within a lens, an eye gesture system was implemented with a sampling frequency of up to 28 Hz. Three discrete eye movements were successfully classified when a participant looked up, right or left using a threshold-based classifier. Moreover, our proof-ofconcept real-time interaction system was tested on 13 participants, who played a simplified Tetris game using their eye movements. Our results show that all participants were successful in completing the game with an average accuracy of 90.8%.

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Robustness of Voltage-induced Magnetocapacitance

Cited by 12 publications

References 65 publications

Observation and theoretical calculations of voltage-induced large magnetocapacitance beyond 330% in MgO-based magnetic tunnel junctions

Observation and theoretical calculations of voltage-induced large magnetocapacitance beyond 330% in MgO-based magnetic tunnel junctions

Large magnetocapacitance beyond 420% in epitaxial magnetic tunnel junctions with an MgAl2O4 barrier

Spintronic Sensors Based on Magnetic Tunnel Junctions for Wireless Eye Movement Gesture Control

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