Measurement of the tilt of a moving domain wall shows precession-free dynamics in compensated ferrimagnets

Haltz, Eloi; Sampaio, João; Krishnia, Sachin; Berges, Léo; Weil, Raphaël; Mougin, A.

doi:10.1038/s41598-020-73049-5

Cited by 24 publications

(14 citation statements)

References 34 publications

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“…We cannot exclude additional contributions as, for example, from inversion symmetry breaking by the (small) concentration gradient in our samples. Experiments on FePt [10] and GdFeCo [29,30] have already shown that a composition gradient can play an important role for the generation of torques [10,24] and "bulk DMI" [29,30] in single layers of such magnetic alloys. In the large family of magnetic rare-earth alloys and other 5d magnetic materials, the existence of these different SOC-based mechanisms related to the absence of inversion symmetry and generating spin currents, spin torques and DMI in single layers in the absence of additional HM layers, is of great interest.…”

Section: Effmentioning

confidence: 99%

“…Such a gradient can break the inversion symmetry and generate a “bulk Rashba effect.” [ 10,22 ] Notably, Dzyaloshinskii–Moriya interactions (DMI), which is another consequence of SOC and lack of inversion symmetry, have been recently observed and related to composition gradients in single layers of GdFeCo. [ 24,29,30 ]…”

Section: Figurementioning

confidence: 99%

“…[10,22] Notably, Dzyaloshinskii-Moriya interactions (DMI), which is another consequence of SOC and lack of inversion symmetry, have been recently observed and related to composition gradients in single layers of GdFeCo. [24,29,30] Before our measurements of torque, in a first set of measurements, we demonstrated the large generation of spin current in GdFeCo by measuring the emitted spin currents in experiments of current-induced modulation of the ferromagnetic resonance (FMR)-linewidth of NiFe in GdFeCo/Cu/NiFe trilayers. The effective global spin Hall angle (sum of SAHEand SHE-like Hall angles) is found to be as large as 0.8.…”

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confidence: 99%

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Current‐Induced Spin Torques on Single GdFeCo Magnetic Layers

et al. 2021

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A novel direction of spintronics, namely "spin-orbitronics", exploits the spin-orbit coupling (SOC) to generate spin currents, which can then induce spin-orbit torques (SOT) to manipulate magnetization. [1] This opens technological applications such as the three-terminal magnetic random memory Spintronics exploit spin-orbit coupling (SOC) to generate spin currents, spin torques, and, in the absence of inversion symmetry, Rashba and Dzyaloshinskii-Moriya interactions. The widely used magnetic materials, based on 3d metals such as Fe and Co, possess a small SOC. To circumvent this shortcoming, the common practice has been to utilize the large SOC of nonmagnetic layers of 5d heavy metals (HMs), such as Pt, to generate spin currents and, in turn, exert spin torques on the magnetic layers. Here, a new class of material architectures is introduced, excluding nonmagnetic 5d HMs, for high-performance spintronics operations. Very strong current-induced torques exerted on single ferrimagnetic GdFeCo layers, due to the combination of large SOC of the Gd 5d states and inversion symmetry breaking mainly engineered by interfaces, are demonstrated. These "self-torques" are enhanced around the magnetization compensation temperature and can be tuned by adjusting the spin absorption outside the GdFeCo layer. In other measurements, the very large emission of spin current from GdFeCo, 80% (20%) of spin anomalous Hall effect (spin Hall effect) symmetry is determined. This material platform opens new perspectives to exert "self-torques" on single magnetic layers as well as to generate spin currents from a magnetic layer.

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Section: Effmentioning

confidence: 99%

Section: Figurementioning

confidence: 99%

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Current‐Induced Spin Torques on Single GdFeCo Magnetic Layers

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“…with σ the energy per unit area of the wall, k B the Boltzmann constant and t the thickness of the sample. Table I shows the values of L c in our system at different temperatures, calculated using the energy σ = 4∆K eff [30] with a typical domain wall width parameter ∆ ≈ 15 nm [31][32][33].…”

Section: B Determination Of the Structure Factor Parametersmentioning

confidence: 99%

Domain-wall roughness in GdFeCo thin films: crossover length scales and roughness exponents

Albornoz,

Guruciaga,

Jeudy

et al. 2021

Preprint

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Domain wall dynamics and spatial fluctuations are closely related to each other and to universal features of disordered systems. Experimentally measured roughness exponents characterizing spatial fluctuations have been reported for magnetic thin films, with values generally different from those predicted by the equilibrium, depinning and thermal reference states. Here, we study the roughness of domain walls in GdFeCo thin films over a large range of magnetic field and temperature. Our analysis is performed in the framework of a model considering length-scale crossovers between the reference states, which is shown to bridge the differences between experimental results and theoretical predictions. We also quantify for the first time the size of the depinning avalanches below the depinning field at finite temperatures.

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“…Secondly, the reduced net angular momentum leads to drastically faster magnetic dynamics. Promising theoretical results and experimental observations have been recently obtained in such multi-lattice magnetic systems [2,3], multi-layers architectures [4][5][6], or synthetic alloys [7][8][9][10][11][12][13]. In particular, it has been * joao.sampaio@universite-paris-saclay.fr shown that the antiferromagnetic coupling between sublattices brings the characteristic frequency of magnetisation dynamics up to the THz range [14][15][16][17][18].…”

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Domain wall dynamics in antiferromagnetically-coupled double-lattice systems

Haltz,

Krishnia,

Berges

et al. 2020

Preprint

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In ferromagnetic materials, the rich dynamics of magnetic domain walls (DWs) under magnetic field or current have been successfully described using the well-known q-ϕ analytical model. We demonstrate here that this simple unidimensional model holds for multiple-sublattice materials such as ferrimagnetic alloys or synthetic antiferromagnets (SAF) by using effective parameters, and is in excellent agreement with double-lattice micromagnetic simulations. We obtain analytical laws for the DW velocity and internal precession angle as a function of net magnetisation for different driving forces (magnetic field, spin transfer and spin-orbit torques) and different propagation regimes in ferrimagnetic alloys and SAFs. The model predicts that several distinctive dynamical features occur near or at the magnetic and the angular compensation points when the net magnetization or the net angular momentum of the system vanishes, and we discuss the experimental observations that have been reported for some of them. Using a higher degree-of-freedom analytical model that accounts for inter-sublattice distortions, we give analytical expressions for these distortions that agree with the micromagnetic simulations. This model shows that the DW velocity and precession rate are independent of the strength of the inter-sublattice exchange coupling, and justifies the use of the simpler effective parameters model.

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Measurement of the tilt of a moving domain wall shows precession-free dynamics in compensated ferrimagnets

Cited by 24 publications

References 34 publications

Current‐Induced Spin Torques on Single GdFeCo Magnetic Layers

Current‐Induced Spin Torques on Single GdFeCo Magnetic Layers

Domain-wall roughness in GdFeCo thin films: crossover length scales and roughness exponents

Domain wall dynamics in antiferromagnetically-coupled double-lattice systems

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