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 Synthetic Antiferromagnet through an fcc Ru Spacer Utilized for Perpendicular Magnetic Tunnel Junctions

Zhang, De Lin; Sun, Congli; Lv, Yang; Schliep, Karl B.; Zhao, Zhengyang; Chen, Junyang; Voyles, Paul M.; Wang, Jian Ping

doi:10.1103/physrevapplied.9.044028

Cited by 24 publications

(5 citation statements)

References 47 publications

(52 reference statements)

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“…This functionality, namely voltage control of the net magnetization, would be desirable in a variety of potential applications, such as dipole-coupled nanomagnetic logic 37,38 , reconfigurable magnonic crystals based on magnetostatic spin waves 39,40 and stray field control and steering of fluid-borne particles 41,42 . By replacing the NiO layer with a stray field biasing layer, the preferred direction of M can instead be fixed, allowing for controlling the orientation of N. We achieved this by integrating an L1 0 -FePd layer with bulk perpendicular magnetic anisotropy 43,44 as a stray field pinning layer (Fig. 5c).…”

Section: Field-free Net Magnetization and Néel Vector Reversalmentioning

confidence: 99%

Voltage control of ferrimagnetic order and voltage-assisted writing of ferrimagnetic spin textures

et al. 2021

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ontrolling the magnetic state of devices by electrical means is critical for spin-based data storage and logic 1,2 . One of the key technological challenges is to achieve efficient 180° magnetic switching by electrical means. Current methods are mostly based on local magnetic fields or spin torques 3,4 . Due to a much lower energy consumption 5,6 , voltage-controlled magnetization switching is desirable. However, it is inherently difficult because electric fields do not induce the required time-reversal symmetry breaking for 180° magnetic switching. Many methods, such as using piezoelectric and multiferroic materials 5,[7][8][9][10][11] , are being explored for voltage-controlled magnetization switching. However, these methods involve either high voltages for inducing enough strain, or difficult fabrication procedures.Multi-sublattice materials present unique opportunities for voltage control of magnetism 12,13 , with ferrimagnets being promising for achieving 180° switching owing to their multi-sublattice configuration with magnetic moments of different magnitudes opposing each other. By tuning the relative sublattice magnetization magnitudes, the net magnetization can be reversed. Moreover, compared with ferromagnets, ferrimagnets offer technological advantages as they allow for small spin textures 14 , fast spin dynamics [14][15][16] and ultrafast optical switching 17 . However, the conventional approaches to controlling the compensation of ferrimagnets, such as varying the composition at fabrication 18 , annealing 19,20 , heating or cooling 21 and hydrogen gas exposure 22,23 , do not allow for localized electrical actuation. Ultrashort light pulses have been shown to enable all-optical switching of ferrimagnets 17,24,25 , however, the need for an ultrafast laser source may complicate device designs and the optical paths may be difficult to scale.Here, we show the reversible control of the dominant sublattice of a rare earth-transition metal (RE-TM) alloy ferrimagnet (GdCo) by a gate voltage (V G ) using a solid-state hydrogen pump 26 . The control originates from the injection of hydrogen, sourced from ambient moisture through hydrolysis, into GdCo, which tunes the relative sublattice magnetizations and hence the degree of compensation. By applying a small V G , the compensation temperature (T M ) can be shifted by >100 K, and the dominant sublattice can be reversibly switched under ambient, isothermal conditions. Element-specific X-ray magnetic circular dichroism (XMCD) revealed that hydrogenation reduces the sublattice magnetization of Gd substantially, but only modestly reduces that of Co. Mean-field modelling of the experimental data combined with ab initio calculations suggest that this results from hydrogen-induced reduction of the inter-sublattice exchange coupling strength that is largely responsible for the Gd sublattice order. We demonstrate here that the dominant sublattice can be toggled using pulses as short as 50 μs at room temperature, and that the devices show no degradation after >10 4 gatin...

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Section: Field-free Net Magnetization and Néel Vector Reversalmentioning

confidence: 99%

Voltage control of ferrimagnetic order and voltage-assisted writing of ferrimagnetic spin textures

et al. 2021

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“…Experimentally such an AFM system can be built as a synthetic antiferromagnet (SAF) [24] where two low-barrier ferromagnets are negatively coupled through RKKY interaction. These superparamagnetic magnets can be realized in a magnetic system where the surface anisotropy counteracts the shape anisotropy [11,25].…”

Section: Magnetization Dynamicsmentioning

confidence: 99%

Subnanosecond Fluctuations in Low-Barrier Nanomagnets

et al. 2019

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Fast magnetic fluctuations due to thermal torques have useful technological functionality ranging from cryptography to probabilistic computing. The characteristic time of fluctuations in typical uniaxial anisotropy magnets studied so far is bounded from below by the well-known energy relaxation mechanism. This time scales as α −1 , where α parameterizes the strength of dissipative processes. Here, we theoretically analyze the fluctuating dynamics in easy-plane and antiferromagnetically coupled nanomagnets. We find in such magnets, the dynamics are strongly influenced by fluctuating intrinsic fields, which give rise to an additional dephasing-type mechanism for washing out correlations. In particular, we establish two time scales for characterizing fluctuations (i) the average time for a nanomagnet to reverse-which for the experimentally relevant regime of low damping is governed primarily by dephasing and becomes independent of α, (ii) the time scale for memory loss of a single nanomagnet-which scales as α −1/3 and is governed by a combination of energy dissipation and dephasing mechanism. For typical experimentally accessible values of intrinsic fields, the resultant thermal-fluctuation rate is increased by multiple orders of magnitude when compared with the bound set solely by the energy relaxation mechanism in uniaxial magnets. This could lead to higher operating speeds of emerging devices exploiting magnetic fluctuations.

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“…As shown in Figure , a typical SAF structure consists of two ferromagnetic (FM) layers separated by a nonmagnetic (NM) layer. These two FM layers are exchange-coupled with individual magnetizations aligned antiparallelly through the Ruderman–Kittel–Kasuya–Yosida (RKKY) interaction. , SAF structures have low stray fields, high stability when exposed to external fields, and extra flexibilities to tune their magnetic properties. , Therefore, SAF materials have been proposed as promising building elements in MTJs, − spin oscillators, and magnonic devices . For SAF, both the damping and the interlayer coupling strength are important properties that affect the dynamics of the system.…”

Section: Representative Examplesmentioning

confidence: 99%

Materials Engineering Enabled by Time-Resolved Magneto-Optical Kerr Effect for Spintronic Applications

Huang

Lattery

Wang

2020

ACS Appl. Electron. Mater.

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As an updated version of the ultrafast pump–probe laser technique, the time-resolved magneto-optical Kerr effect (TR-MOKE) methodology enables the detection of magnetization dynamics with superb temporal (sub-picosecond) and spatial (diffraction-limited beam spot) resolutions. It is a powerful tool to characterize material properties and to reveal the rich physics of magnetization dynamics in magnetic thin films, which serve as the essential building blocks for spintronic and magnetic recording devices. In this spotlight article, we will highlight the recent advances in the development of TR-MOKE metrology and its applications for capturing the magnetization dynamics in technologically important spintronic materials. We cover several representative examples based on research activities carried out at the University of Minnesota (UMN), including studies of Gilbert damping, spin-strain coupling, and interlayer exchange coupling of perpendicular magnetic materials. A brief discussion will be also presented, which highlights several other emerging research topics that are potentially enabled by this metrology to form a more comprehensive picture of its applications for emerging materials and technologies.

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L10 Fe−Pd Synthetic Antiferromagnet through an fcc Ru Spacer Utilized for Perpendicular Magnetic Tunnel Junctions

Cited by 24 publications

References 47 publications

Voltage control of ferrimagnetic order and voltage-assisted writing of ferrimagnetic spin textures

Voltage control of ferrimagnetic order and voltage-assisted writing of ferrimagnetic spin textures

Subnanosecond Fluctuations in Low-Barrier Nanomagnets

Materials Engineering Enabled by Time-Resolved Magneto-Optical Kerr Effect for Spintronic Applications

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