Brownian motion of skyrmion bubbles and its control by voltage applications

Nozaki, Takayuki; Jibiki, Yuma; Goto, Minori; Tamura, E.; Nozaki, Tomohiro; Kubota, Hiroshi; Fukushima, Akio; Yuasa, Shinji; Suzuki, Y.

doi:10.1063/1.5070101

Cited by 88 publications

(62 citation statements)

References 26 publications

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“…In addition to ultrathin epitaxial films with large PMA [35,59,60,61,62,63,64,65,66,67], VCMA effects have been observed in various materials systems, for example, in sputter-deposited CoFeB [68,69,70,71,72,73,74,75,76,77,78,79,80,81], which is an important practical material that is used in the mass production of MTJs, and in self-assembled nano-islands [82], nanocomposite structures [83], and ultrathin layers with quantum well states [84]. The VCMA effect can also be applied for the control of domain wall motion [85,86,87] and magnetic skyrmions [88,89,90]. In addition, voltage control of the magnetic properties has been expanded not only for the PMA, but also for the Curie temperature [22], Dzyaloshinskii-Moriya interactions [91], interlayer exchange coupling [92], and proximity-induced magnetism in non-magnetic metal thin films [93,94,95].…”

Section: Overview Of the Vcma Effect And Voltage-induced Dynamic Smentioning

confidence: 99%

Recent Progress in the Voltage-Controlled Magnetic Anisotropy Effect and the Challenges Faced in Developing Voltage-Torque MRAM

et al. 2019

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The electron spin degree of freedom can provide the functionality of “nonvolatility” in electronic devices. For example, magnetoresistive random access memory (MRAM) is expected as an ideal nonvolatile working memory, with high speed response, high write endurance, and good compatibility with complementary metal-oxide-semiconductor (CMOS) technologies. However, a challenging technical issue is to reduce the operating power. With the present technology, an electrical current is required to control the direction and dynamics of the spin. This consumes high energy when compared with electric-field controlled devices, such as those that are used in the semiconductor industry. A novel approach to overcome this problem is to use the voltage-controlled magnetic anisotropy (VCMA) effect, which draws attention to the development of a new type of MRAM that is controlled by voltage (voltage-torque MRAM). This paper reviews recent progress in experimental demonstrations of the VCMA effect. First, we present an overview of the early experimental observations of the VCMA effect in all-solid state devices, and follow this with an introduction of the concept of the voltage-induced dynamic switching technique. Subsequently, we describe recent progress in understanding of physical origin of the VCMA effect. Finally, new materials research to realize a highly-efficient VCMA effect and the verification of reliable voltage-induced dynamic switching with a low write error rate are introduced, followed by a discussion of the technical challenges that will be encountered in the future development of voltage-torque MRAM.

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Section: Overview Of the Vcma Effect And Voltage-induced Dynamic Smentioning

confidence: 99%

Recent Progress in the Voltage-Controlled Magnetic Anisotropy Effect and the Challenges Faced in Developing Voltage-Torque MRAM

et al. 2019

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“…An appealing and well-studied topological spin texture is the magnetic skyrmion in perpendicularly magnetized system, the existence of which was theoretically predicted in 1989 [11,12], and was experimentally observed in 2009 [13]. Since the first experimental observation, magnetic skyrmions have been extensively studied due to their particle-like nature [14,15] and large potential in advanced electronic and spintronic applications [16][17][18][19][20][21][22][23][24][25][26][27][28][29][30]. So far, the creation, annihilation and manipulation of magnetic skyrmions have been realized in magnetic multilayers at room temperature [18][19][20][22][23][24][25][26][27][28][29][30], and a lot of skyrmion-based device applications have been proposed [31][32][33][34][35][36][37][38][39][40][41][42] and even demonstrated in roomtemperature experiments [43]<...>…”

Section: Introductionmentioning

confidence: 99%

Static and dynamic properties of bimerons in a frustrated ferromagnetic monolayer

et al. 2020

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Magnetic bimeron is a topological counterpart of skyrmions in in-plane magnets, which can be used as spintronic information carrier. We report the static properties of bimerons with different topological structures in a frustrated ferromagnetic monolayer, where the bimeron structure is characterized by the vorticity Qv and helicity η. It is found that the bimeron energy increases with Qv, and the energy of an isolated bimeron with Qv = ±1 depends on η. We also report the dynamics of frustrated bimerons driven by the spin-orbit torques, which depend on the strength of the damping-like and field-like torques. We find that the isolated bimeron with Qv = ±1 can be driven into linear or elliptical motion when the spin polarization is perpendicular to the easy axis. We numerically reveal the damping dependence of the bimeron Hall angle driven by the damping-like torque. Besides, the isolated bimeron with Qv = ±1 can be driven into rotation by the damping-like torque when the spin polarization is parallel to the easy axis. The rotation frequency is proportional to the driving current density. In addition, we numerically demonstrate the possibility of creating a bimeron state with a higher or lower topological charge by the current-driven collision and merging of bimeron states with different Qv. Our results could be useful for understanding the bimeron physics in frustrated magnets.

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“…However, the experimental reported driven current is above 10 10 − 10 11 A/m 232, 34,36 , not too far from the typical magnetic domain wall driving current and far above the community's expectation. Skyrmions can also perform a random-walk-like motion in disordered system 49 . All these issues and more need detail analysis and a better understanding.…”

Section: Introductionmentioning

confidence: 99%

Current-driven skyrmion motion in granular films

2020

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Current-driven skyrmion motion in random granular films is investigated with interesting findings. For a given current, there exists a critical disorder strength below which its transverse motion could either be boosted below a critical damping or be hindered above the critical damping, resulting in current and disorder dependences of skyrmion Hall angle. The boosting comes mainly from the random force that is opposite to the driving force (current). The critical damping depends on the current density and disorder strength. However, the longitudinal motion of a skyrmion is always hindered by the disorder. Above the critical disorder strength, skyrmions are pinned. The disorder-induced random force on a skyrmion can be classified as static and kinetic ones, similar to the friction force in the Newtonian mechanics. In the pinning phase, the static (pinning) random force is transverse to the current density. The kinetic random force is opposite to the skyrmion velocity when skyrmions are in motion. Furthermore, we provide strong evidences that the Thiele equation can perfectly describe skyrmion dynamics in granular films. These findings provide insight to skyrmion motion and should be important for skyrmiontronics.

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Brownian motion of skyrmion bubbles and its control by voltage applications

Cited by 88 publications

References 26 publications

Recent Progress in the Voltage-Controlled Magnetic Anisotropy Effect and the Challenges Faced in Developing Voltage-Torque MRAM

Recent Progress in the Voltage-Controlled Magnetic Anisotropy Effect and the Challenges Faced in Developing Voltage-Torque MRAM

Static and dynamic properties of bimerons in a frustrated ferromagnetic monolayer

Current-driven skyrmion motion in granular films

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