Simultaneous control of magnetic topologies for reconfigurable vortex arrays

Im, Mi‐Young; Fischer, Peter; Han, Hee‐Sung; Vogel, Andreas; Jung, Minkyung; Chao, Weilun; Meier, Guido; Hong, Jung‐Il; Lee, Ki-Suk

doi:10.1038/am.2016.199

Cited by 20 publications

(11 citation statements)

References 43 publications

(64 reference statements)

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“…This work demonstrates that ultrafast dynamics at the initial stage of vortex creation can be a decisive factor for the stochastic nature in the formation of vortex structures in asymmetric nanodisks and the stochasticity in the vortex formation process can be controlled by adjusting the geometrical parameter of disk arrays such as interdisk distance [17][18][19].…”

Section: Formation Of Magnetic Vortex Structures In Nanodisksmentioning

confidence: 90%

“…In this article, previous works on stochastic natures of various magnetic processes such as domain nucleation and reversal process in ultrathin CoCrPt alloy films [13,14], the domain-wall motions in Ni 80 Fe 20 notched nanowires [15,16], and the creation of vortex structure in Ni 80 Fe 20 nanodisks [17][18][19] studied by soft X-ray microscopy are reviewed. A primary factor affecting the stochasticity in each magnetic process and the approach how to control the intrinsic character, stochastic nature are further discussed.…”

Section: Introductionmentioning

confidence: 99%

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Stochastic nature of magnetic processes studied by full-field soft X-ray microscopy

2018

Current Applied Physics

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In nanomagnetism, one of the crucial scientific questions is whether magnetic behaviors are deterministic or stochastic on a nanoscale. Apart from the exciting physical issue, this question is also of paramount highest relevance for using magnetic materials in a wealth of technological applications such as magnetic storage and sensor devices. In the past, the research on the stochasticity of a magnetic process has been mainly done by macroscopic measurements, which only offer ensemble-averaged information. To give more accurate answer for the question and to fully understand related underlying physics, the direct observation of statistical behaviors in magnetic structures and magnetic phenomena utilizing advanced characterization techniques is highly required. One of the ideal tools for such study is a full-field soft X-ray microscope since it enables imaging of magnetic structures on the large field of view within a few seconds. Here we review the stochastic behaviors of various magnetic processes including magnetization reversal process in thin films, magnetic domain wall motions in nanowires, and magnetic vortex formations in nanodisks studied by full-field soft X-ray microscopy. The origin triggering the stochastic nature witnessed in each magnetic process and the way to control the intrinsic nature are also discussed.

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Section: Formation Of Magnetic Vortex Structures In Nanodisksmentioning

confidence: 90%

Section: Introductionmentioning

confidence: 99%

Stochastic nature of magnetic processes studied by full-field soft X-ray microscopy

2018

Current Applied Physics

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“…In the applications, reproducibility and controllability of magnetization switching of the individual magnetic elements is a highly desirable feature. [15][16][17] So far, most experimental studies on switching processes in magnetic arrays have used macroscopic analytical tools such as assemble-averaged hysteresis loops over large arrays of magnetic disks 18,19 due to limitations in conventional magnetic microscopy techniques. To address the stochasticity issue of the magnetization switching of a single magnetic element in arrays, [20][21][22]…”

Section: Introductionmentioning

confidence: 99%

Stochasticity in the Switching of Nanodisks for Probabilistic Computing

Han

Lee

et al. 2021

ACS Appl. Nano Mater.

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Stochasticity in magnetic nanodevices is an essential characteristic for harnessing those devices to computing based on population coding or the building blocks of probabilistic computing, pbits. A magnetic tunneling junction (MTJ) consisting of a patterned magnetic element is considered as a promising computing unit in the concept of artificial neurons and p-bits. The comprehensive understanding of the stochasticity in the switching of patterned magnetic elements is crucial for realizing MTJ based probabilistic computing technology. In the present work, the stochastic behavior in switching process of a perpendicularly magnetized Co/Pt disk within an array was directly observed utilizing full-field soft X-ray microscopy. Within 50 repeated hysteretic cycles, the stochastic magnetization switching of individual Co/Pt disks within disk arrays is identified. We found that the stochasticity in the magnetization switching of disks considerably depends on the disk size. The stochasticity initially decreases as the disk radius gets bigger from 125 nm to 375 nm (Region I), then increases with further enlarging disk size to 625 nm (Region II). The variance of thermal fluctuation relevant to the disk size and the multi-level switching within a disk are severely involved in the observed size dependent stochasticity. This work provides the way for controlling the stochasticity in the switching of nanopatterned elements, which is a key aspect for MTJ-based probabilistic computing.

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“…In patterned soft magnetic materials, magnetic vortex and antivortex are representative topologically non-trivial magnetic structures, 4,[9][10][11][12][13][14][15][16] which provide a unique playground for fundamental study on non-trivial nano-spin behavior. They are composed of in-plane swirling magnetic components and out-of-plane (OOP) cores.…”

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confidence: 99%

Topology-dependent stability of vortex-antivortex structures

Han

Lee

Jung

et al. 2021

Applied Physics Letters

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The non-trivial topology of magnetic structures such as vortices and skyrmions is considered as a key concept to explain the stability of those structures. The stability, dictated by non-trivial topology, provides great potential for device applications. Although it is a very critical scientific and technological issue, it is elusive to experimentally study the topologydependent stability owing to the difficulties in establishing stably formed magnetic structures with different topologies. Here, we establish a platform for vortex-antivortex structures with different topological charges within Ni 80 Fe 20 rectangular elements thick enough to stabilize a unique three-dimensional magnetic structure with non-uniform magnetization along the thickness of the elements. The detailed magnetization configurations of the three-dimensional vortex-antivortex structures and their annihilations during their field-driven motions are investigated by utilizing magnetic transmission soft x-ray microscopy and micromagnetic simulation. We demonstrate that the stability of vortex-antivortex structures significantly depends on their topologies and the topology-dependent stability is associated with their different annihilation mechanisms. We believe that this work provides in-depth insight into the stability of magnetic structures and its topology dependence.

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Simultaneous control of magnetic topologies for reconfigurable vortex arrays

Cited by 20 publications

References 43 publications

Stochastic nature of magnetic processes studied by full-field soft X-ray microscopy

Stochastic nature of magnetic processes studied by full-field soft X-ray microscopy

Stochasticity in the Switching of Nanodisks for Probabilistic Computing

Topology-dependent stability of vortex-antivortex structures

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