Effects of substitution on the exchange stiffness and magnetization of Co films

Eyrich, C.; Zamani, Atieh; Huttema, Wendell; Arora, Manoj K.; Harrison, D. A.; Rashidi, F.; Broun, D. M.; Heinrich, B.; Mryasov, O. N.; Ahlberg, Martina; Karis, Olof; Jönsson, Petra E.; From, M.; Zhu, Xiaobin; Girt, Erol

doi:10.1103/physrevb.90.235408

Cited by 51 publications

(30 citation statements)

References 42 publications

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“…The d 0 value seems to be reasonable compared to the data on A ex in Ref. [25] (estimated value of d 0 ≈ 4.3 nm). However, the value for D sw,∞ , i.e., for bulk Co, is almost a factor of 3 higher than the expected value of 340 ± 75 meVÅ 2 found for polycrystalline Co [26].…”

Section: A Spin Current Absorption and Thz Spin Wave Excitationsupporting

confidence: 85%

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Absorption and generation of femtosecond laser-pulse excited spin currents in noncollinear magnetic bilayers

Lalieu

Koopmans

2017

Phys. Rev. B

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Spin currents can be generated on an ultrafast time scale by excitation of a ferromagnetic (FM) thin film with a femtosecond laser pulse. Recently, it has been demonstrated that these ultrafast spin currents can transport angular momentum to neighboring FM layers, being able to change both the magnitude and orientation of the magnetization in the adjacent layer. In this paper, both the generation and absorption of these optically excited spin currents are investigated. This is done using noncollinear magnetic bilayers, i.e., two FM layers separated by a conductive spacer. Spin currents are generated in a Co/Ni multilayer with out-of-plane (OOP) anisotropy, and absorbed by a Co layer with an in-plane (IP) anisotropy. This behavior is confirmed by careful analysis of the laser-pulse induced magnetization dynamics, whereafter it is demonstrated that the transverse spin current is absorbed very locally near the injection interface of the IP layer (90% within the first ≈2 nm). Moreover, it will also be shown that this local absorption results in the excitation of THz standing spin waves within the IP layer. The dispersion measured for these high-frequency spin waves shows a discrepancy with respect to the theoretical predictions, for which an explanation involving intermixed interface regions is proposed. Lastly, the spin current generation is investigated by using magnetic bilayers with a different number of repeats for the Co/Ni multilayer, which proves to be of great relevance for identifying the optical spin current generation mechanism.

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Section: A Spin Current Absorption and Thz Spin Wave Excitationsupporting

confidence: 85%

“…Since the data presented in Ref. [25] suggest an exponential dependence of A ex on the Co thickness, the following estimation is used,…”

Section: A Spin Current Absorption and Thz Spin Wave Excitationmentioning

confidence: 99%

Absorption and generation of femtosecond laser-pulse excited spin currents in noncollinear magnetic bilayers

Lalieu

Koopmans

2017

Phys. Rev. B

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“…As a result, A is calculated to be (6.5 ± 0.5) × 10 −12 J/m at 300 K. This value is considerably smaller than a more typical value of 2 × 10 −11 J/m found in, for instance, a Ta/CoFeB/MgO structure [30]. The difference is likely to be caused by the intermixing of Ru and CoFeB, which has been shown to reduce both A and M s in Co/Ru multilayers [31]. Due to the existence of models relating the width of magnetic stripe domains in perpendicular samples to the strength of the DMI, we collected a series of stripe domain images at various temperatures using high-resolution XMCD-PEEM, one of which is shown in Fig.…”

Section: -2mentioning

confidence: 68%

Temperature dependence of the Dzyaloshinskii-Moriya interaction in ultrathin films

et al. 2020

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The Dzyaloshinskii-Moriya interaction gives rise to a chiral exchange between neighboring spins in the technologically relevant class of perpendicularly magnetized ultrathin film materials. In this paper, we study the temperature dependence of the Dzyaloshinskii-Moriya interaction based on extensive characterization of a thin film which hosts a skyrmion state using both bulk magnetometry and x-ray magnetic circular dichroism photoemission electron microscopy. A version of the Bloch law explicitly for thin film geometries is derived to extract the exchange stiffness. The strength of the Dzyaloshinskii-Moriya interaction, D, is found to have a dependence on the saturation magnetization, M s of D ∝ M 1.86±0.16 s . Further, by extracting the uniaxial anisotropy K u and the exchange stiffness A, we find that D ∝ K 1.02±0.11 u and D ∝ A 0.95±0.07 . Skyrmion radii are also used to extract the strength of the Dzyaloshinskii-Moriya interaction which is compared to that derived from measurements of stripe domains. The origins of the correlations between material parameters are discussed and consequences of these relationships for skyrmion devices are considered.

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“…According to the latter 38,39,40 , the DMI parameter can be roughly expressed as = 2 R , where A is the exchange stiffness and R = 2 R ℏ 2 is determined by the Rashba coefficient, R , and effective electron mass, me. The latter in Co was measured to be about 0.45 m0 41 (with m0 being the rest mass of electron), and the exchange stiffness, A, was found to be about 15.5 ×10 -12 J/m 32,42 . The Rashba coefficient, R , can then be extracted from αR=2E0/k0, where E0 is the Rashba splitting at the wave vector k0.…”

Section: First-principles Calculationsmentioning

confidence: 99%

Significant Dzyaloshinskii–Moriya interaction at graphene–ferromagnet interfaces due to the Rashba effect

et al. 2018

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The possibility of utilizing the rich spin-dependent properties of graphene has attracted much attention in the pursuit of spintronics advances. The promise of high-speed and low-energy-consumption devices motivates the search for layered structures that stabilize chiral spin textures such as topologically protected skyrmions. Here we demonstrate that chiral spin textures are induced at graphene/ferromagnetic metal interfaces. Graphene is a weak spin-orbit coupling material and is generally not expected to induce a sufficient Dzyaloshinskii-Moriya interaction to affect magnetic chirality. We demonstrate that indeed graphene does induce a type of Dzyaloshinskii-Moriya interaction due to the Rashba effect. First-principles calculations and experiments using spin-polarized electron microscopy show that this graphene-induced Dzyaloshinskii-Moriya interaction can have a similar magnitude to that at interfaces with heavy metals. This work paves a path towards two-dimensional-material-based spin-orbitronics.

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Effects of substitution on the exchange stiffness and magnetization of Co films

Cited by 51 publications

References 42 publications

Absorption and generation of femtosecond laser-pulse excited spin currents in noncollinear magnetic bilayers

Absorption and generation of femtosecond laser-pulse excited spin currents in noncollinear magnetic bilayers

Temperature dependence of the Dzyaloshinskii-Moriya interaction in ultrathin films

Significant Dzyaloshinskii–Moriya interaction at graphene–ferromagnet interfaces due to the Rashba effect

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