Compositional gradient induced enhancement of Dzyaloshinskii–Moriya interaction in Pt/Co/Ta heterostructures modulated by Pt–Co alloy intralayers

Park, Junho; Kim, Tae Hyun; Kim, Gyu Won; Bessonov, V. D.; Telegin, А. V.; Iliushin, Ilia G.; Pervishko, Anastasiia A.; Yudin, Dmitry; Samardak, Aleksei Yu.; Ognev, Alexey V.; Samardak, Alexander S.; Cho, Jiung; Kim, Young Keun

doi:10.1016/j.actamat.2022.118383

Cited by 9 publications

(4 citation statements)

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“…Most of the papers investigating micromagnetic features in Co-Pd based films consider multilayer structures with sharp interfaces and pre-set Co versus Pd composition (either pure Co/Pd multilayer or CoPd solid solutions with digital content variation). [21][22][23][24]58] Smaller number of papers is considered slightly mixed layers with an intermediate 4-6 monolayer thick area. [26,59,60] Unlike the majority of the papers, the structures in the present study are highly intermixed Co x Pd 1-x films with unfixed Co versus Pd content.…”

Section: Resultsmentioning

confidence: 99%

Exotic Topological Magnetic States in Thin Co/Pd Ferromagnetic Films

Dorokhin,

Ved,

Kalentyeva

et al. 2024

Annalen der Physik

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Thin ferromagnet/heavy metal multilayer films are considered as prospective media for a magnetic recording and Co/Pd films are a good example of such materials. In this work, the magnetic properties and micromagnetic structure of Co/Pd multilayer films are studied with different bilayer thicknesses ([Co(0.3 × t nm)/Pd(0.5 × t nm)]10), but with the same ratio Co versus Pd. Transmission electron microscope and X‐ray diffraction studies allow authors to suppose that the investigated films are highly mixed alloys. Magnetic force microscopy and Lorentz transmission electron microscopy showed the presence of various micromagnetic features in the films. Along with skyrmions that are well‐known magnetic topological artifacts some new features are revealed, which are interpreted as 360° domain walls, skyrmioniums and the combination of the above two. It is found that the type and density of micromagnetic features strongly depend on the bilayer thickness parameter (t). The effect is associated with the peculiarities of interfacial magnetic interactions in the samples with highly mixed interfaces. The tooling coefficient represents a useful tool of the electron beam evaporation technique enabling wide manipulation of micromagnetic particles, in particular, skyrmioniums that are currently considered a prospective media for current driven magnetic recording.

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Section: Resultsmentioning

confidence: 99%

Exotic Topological Magnetic States in Thin Co/Pd Ferromagnetic Films

Dorokhin,

Ved,

Kalentyeva

et al. 2024

Annalen der Physik

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“…The effective field in CoTbPt has been proposed to have originated from the inversion symmetry-breaking by introducing the vertical gradient compositions of Pt, which, in combination with SOT, can lead to the deterministic field-free SOT switching in the absence of an external field. − When there is a composition gradient of Pt in the ferrimagnetic layer, it can induce a gradient-driven bulk Dzyaloshinskii–Moriya interaction (b-DMI). While the b-DMI is defined by the presence of composition differences and structure symmetry which can break the chiral symmetry and determine the SOT switching without an external field. , The absence of SOT switching at H x = −13 Oe indicates the effective field of −13 Oe, which is canceled by the external field and results in the nondeterministic SOT switching. It is worth noticing that the switching ratio of R Hall is gradually reduced at a larger H x , i.e., a multi-state behavior.…”

Section: Resultsmentioning

confidence: 99%

“…The present experiment also indicates that the magnitude of the effective structure symmetry which can break the chiral symmetry and determine the SOT switching without an external field. 52,53 The absence of SOT switching at H x = −13 Oe indicates the effective field of −13 Oe, which is canceled by the external field and results in the nondeterministic SOT switching. It is worth noticing that the switching ratio of R Hall is gradually reduced at a larger H x , i.e., a multi-state behavior.…”

Section: ■ Introductionmentioning

confidence: 99%

Field-Free SOT-Switching Based on a Vertical Composition Gradient of Ferrimagnetic Alloys

Zeng,

Wen,

et al. 2023

ACS Appl. Electron. Mater.

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Reproducible field-free spin–orbit torque (SOT)-driven perpendicular magnetization switching is essential for the development of ultralow-power spintronic devices. However, the perpendicular magnetization of bulk-symmetric monolayer ferromagnetic films cannot be switched directly by the current-induced SOT. An additional auxiliary in-plane magnetic field is required to realize deterministic switching, which is unfavorable for device applications. Here, we break the bulk-center symmetry of CoTb alloy films by introducing a vertical composition gradient of heavy metal Pt, and we thus achieve the field-free SOT switching. The experimental results also show that the vertical composition gradient of Pt in the magnetic layer induces an out-of-plane effective field, and the magnitude of this effective field is proportional to the Pt vertical composition gradient. The data also revealed the presence of the multilevel resistance state, which is consistent with the requirements of artificially intelligent neuro-synapses. This field-free multilevel resistive state provides a way for the design of resistive elements of neural network structures.

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“…Recently, the Dzyaloshinskii–Moriya interaction (DMI) has gained much attention since it is recognized to play an essential role in a broad range of physical phenomena, such as the observation of magnetic skyrmions, − fast current-controlled domain wall motion, , magnetoelectric effect, , topological Hall effect, and magnetization switching. , The emergence of DMI requires the breaking of inversion symmetry in the spin system with spin–orbit coupling (SOC). , In magnetic multilayers, it is usually believed that the disorders like the intermixing and dusting of elements at interfaces are detrimental to the interfacial DMI. , Interestingly, recent experiments − have observed a significant DMI (termed g-DMI hereafter) in the amorphous thin films with a composition gradient to break the inversion symmetry. The measured DMI value shows a linear relation with the film thickness, signifying a bulk nature of g-DMI despite in the thin films.…”

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confidence: 99%

Gradient-Induced Dzyaloshinskii–Moriya Interaction

et al. 2022

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The Dzyaloshinskii−Moriya interaction (DMI) that arises in the magnetic systems with broken inversion symmetry plays an essential role in topological spintronics. Here, by means of atomistic spin calculations, we study an intriguing type of DMI (g-DMI) that emerges in the films with composition gradient. We show that both the strength and chirality of g-DMI can be controlled by the composition gradient even in the disordered system. The layerresolved analysis of g-DMI unveils its additive nature inside the bulk layers and clarifies the linear thickness dependence of g-DMI observed in experiments. Furthermore, we demonstrate the g-DMI-induced chiral magnetic structures, such as spin spirals and skyrmions, and the g-DMI driven field-free spin−orbit torque (SOT) switching, both of which are crucial toward practical device application. These results elucidate the underlying mechanisms of g-DMI and open up a new way to engineer the topological magnetic textures.

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Compositional gradient induced enhancement of Dzyaloshinskii–Moriya interaction in Pt/Co/Ta heterostructures modulated by Pt–Co alloy intralayers

Cited by 9 publications

References 50 publications

Exotic Topological Magnetic States in Thin Co/Pd Ferromagnetic Films

Exotic Topological Magnetic States in Thin Co/Pd Ferromagnetic Films

Field-Free SOT-Switching Based on a Vertical Composition Gradient of Ferrimagnetic Alloys

Gradient-Induced Dzyaloshinskii–Moriya Interaction

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