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[IEEE 2018 International Conference on Simulation of Semiconductor Processes and Devices (SISPAD) - Austin, TX (2018.9.24-2018.9.26)] 2018 International Conference on Simulation of Semiconductor Processes and Devices (SISPAD) - FANTASI: A Novel Devices-to-Circuits Simulation Framework for Fast Estimation of Write Error Rates in Spintronics
摘要： Though physical mechanisms such as spin-transfer torque (STT), spin-orbit torque (SOT), and voltage-controlled magnetic anisotropy (VCMA) has potential to enable energy-efficient and ultra-fast switching of spintronic devices, the switching dynamics are stochastic due to thermal fluctuations. Thus, there is a need in spintronics to understand the interactions between circuit design and the error rate in the switching mechanism, called as write error rate. In this paper, we propose a novel devices-to-circuits simulation framework (FANTASI) for fast estimation of the write error rates (WER) in different spintronic devices and circuits. Here, we show that, FANTASI enables efficient spintronic device-circuit co-design, with results in good agreement with the experimental measurements.
关键词： Fokker-Planck equation,spin-orbit torque,Spin-transfer torque,voltage-controlled magnetic anisotropy,spintronics
更新于2025-09-23 15:22:29
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Influence of the capping layer material on the interfacial Dzyaloshinskii-Moriya interaction in Pt/Co/capping layer structures probed by Brillouin light scattering<sup></sup>
摘要： Influence of the capping layer material on the interfacial Dzyaloshinskii-Moriya interaction in Pt/Co/capping layer structures probed by Brillouin light scattering. Co ultrathin films, of various thicknesses (0.8 nm ≤ tCo ≤ 2.5 nm), have been grown by sputtering on Si substrates, using Pt buffer layers and different capping layers (Cu, Ir, MgO and Pt). The x-ray diffraction revealed that our films have a (111) out-of-plane texture with various degrees of strains. Their magnetic properties have been studied by vibrating sample magnetometry (VSM) and Brillouin light scattering (BLS) in the Damon-Eshbach geometry. VSM characterizations revealed that films with Co thickness below (above) the spin reorientation transition thickness, which is capping layer dependent, are perpendicularly (in-plane) magnetized, suggesting the existence of an interface anisotropy. The magnetic dead layer has been taken into account to precisely determine the surface anisotropy constant was found to be 1.42 ± 0.02 erg/cm2 and of 1.33 ± 0.02 erg/cm2 for the Pt/Co/Cu and Pt/Co/Ir samples, respectively, suggesting that it is due to the Pt/Co interface and that the top Co/Cu or Co/Ir interfaces have a negligible contribution. A lower value of 1.07 ± 0.02 erg/cm2 has been obtained for Pt/Co/MgO most probably due to over-oxidation of Co at the Co/MgO interface. The BLS measurements revealed a pronounced nonreciprocal spin waves propagation, due to the interfacial Dzyaloshinskii-Moriya interaction (iDMI) induced by Pt interface with Co, which increases with decreasing Co thickness. The surface iDMI constant Ds estimated at -0.8 pJ/m, -1.05 pJ/m and –0.95 pJ/m, respectively for Pt/Co/Ir, Pt/Co/Cu and Pt/Co/MgO for the samples where a linear thickness dependence of the effective iDMI constant has been observed.
关键词： Dzyaloshinskii-Moriya interaction,Brillouin light scattering,spin waves and Perpendicular magnetic anisotropy,Interface effects
更新于2025-09-23 15:22:29
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Extreme asymmetry of Néel domain walls in multilayered films of the dilute magnetic semiconductor (Ga,Mn)(As,P)
摘要： We report on unconventional perfectly shaped, fully asymmetric ～90? Néel domain walls in multilayered ?lms of the diluted ferromagnetic semiconductor (Ga,Mn)(As,P) with a stepwise variation of P doping. Our results contradict micromagnetic calculations, which favor symmetric domain walls due to crystallographic anisotropy and stray ?eld energy. We demonstrate that both the puzzling uniaxial in-plane anisotropy in the tetragonal multilayered ?lm and the asymmetry of the domain walls could result from Dzyaloshinskii-Moriya interactions that are enhanced by the multiple sharp interfaces between the layers and from anisotropic nonrelativistic exchange coupling. Our ?nding shows that digital variations of composition during the molecular beam epitaxy can be used to tune the anisotropy and chirality of magnetic multilayers.
关键词： diluted magnetic semiconductor,Dzyaloshinskii-Moriya interactions,magnetic anisotropy,Néel domain walls,molecular beam epitaxy
更新于2025-09-23 15:21:01
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films
摘要： We report proximity effects of spin-orbit coupling in EuO1?x ?lms capped with a Pt overlayer. Transport measurements suggest that current ?ows along a conducting channel at the interface between the Pt and EuO. The temperature dependence of the resistivity picks up the critical behaviors of EuO, i.e., the metal-to-insulator transition. We also ?nd an unusual enhancement of the magnetic anisotropy in this structure from its bulk value, which results from strong spin-orbit coupling across the Pt/EuO1?x interface.
关键词： magnetic anisotropy,Pt/EuO interface,spin-orbit coupling,transport properties
更新于2025-09-23 15:21:01
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Underlayer dependence of electric field effect on magnetic anisotropy and its volatility in CoFeB/MgO structures
摘要： We report the dependence of voltage-controlled magnetic anisotropy (VCMA) effect and its volatility on an underlayer (UL) in CoFeB/MgO structures. For a sample with Ta or Pt UL, the VCMA effect occurs when the applied gate voltage (Vg) exceeds a critical value, and it persists even after removing Vg. This is in contrast to the volatile VCMA effect and its linear dependence on Vg in a sample with W UL. Furthermore, we demonstrate that the volatility of the VCMA effect can be modified by introducing a Ta/W bilayer, enabling arbitrary control of the magnetic properties via VCMA effect.
关键词： Voltage controlled magnetic anisotropy,Underlayer dependence,Perpendicular magnetic anisotropy,Electric-field effect
更新于2025-09-19 17:15:36
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Annealing effect on laser-induced magnetization dynamics in Co/Ni-based synthetic antiferromagnets with perpendicular magnetic anisotropy
摘要： We report a comprehensive study of annealing treatment modulation on the laser-induced ultrafast magnetic behaviors in antiferromagnetically exchange-coupled [Ni/Co]4/Ru/[Co/Ni]3 multilayers with perpendicular magnetic anisotropy (PMA). Magnetic hysteresis loops indicate that the uniaxial PMA ?eld Hkeff decreases monotonously with the increase in annealing temperature Ta, but the variation of interlayer coupling ?eld Hex is rather complicated. Time-resolved magnetic-optical Kerr effect (MOKE) measurements demonstrate that the laser-excited demagnetization and precession process relies signi?cantly on Ta. Upon laser impulsion, the MOKE signal immediately shows a nonchanging transient increase and decrease with H increasing for low Ta, but only the ultrafast decreasing behavior for high Ta. From the subsequent dynamic precession spectra, the optical and acoustic precession modes are identi?ed. By ?tting the ?eld-dependent frequency curves via the deduced dispersion relations, both Hkeff and Hex are determined and their variation trends agree well with the results from the static magnetic measurement. Moreover, it is found that the critical ?eld where the ultrafast signal decrease occurs is dependent on the co-effect of Hkeff and Hex, whereas the maximum ?eld at which the optical mode precession disappears shares the same trend as Hex. The magnetic damping of acoustic mode is seen to increase with Ta due to the increased inhomogeneities. Our ?ndings provide a deep understanding of the magnetic properties in synthetic antiferromagnetic multilayers with high annealing temperatures, which will be helpful for designing advanced spintronic devices.
关键词： time-resolved magnetic-optical Kerr effect,laser-induced ultrafast magnetic behaviors,annealing treatment,synthetic antiferromagnets,perpendicular magnetic anisotropy
更新于2025-09-16 10:30:52
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Precession damping in [Co <sub/>60</sub> Fe <sub/>40</sub> /Pt] <sub/>5</sub> multilayers with varying magnetic homogeneity investigated with femtosecond laser pulses
摘要： We report on the ultrafast magnetization dynamics of [Co60Fe40/Pt]5 multilayers studied with femtosecond laser pulses. The samples were grown at room temperature by DC magnetron sputtering with Ta capping and Pt buffer layers and present the same thickness and perpendicular magnetic anisotropy as determined by vibrating sample magnetometry. Controlled growth rate of the Pt buffer layer modified the anisotropy fields and magnetic domain sizes as measured by magnetic force microscopy (MFM). An estimation of the average magnetic domain sizes was obtained from the profile of the self-correlation transform of the MFM images. For multilayers having an average magnetic domain size of 490 nm, we report a damped precession of the magnetization which decays with a time constant of ～100 ps and which has a frequency which varies from 8.4 GHz to 17.0 GHz as the external field increases from 192 mT to 398 mT. Fitting the precession dynamics with the Landau-Lifshitz-Gilbert equation we evaluated the damping α, which decreases from 0.18 to 0.05 with increasing magnetic domain sizes (127 nm to 490 nm). These α values are higher than for single layers suggesting an enhanced scattering and spin pumping effects from the Pt adjacent layers. In addition, the precession frequency increases from 2.04 GHz to 11.50 GHz as the anisotropy field of the multilayers increases from 6.5 kOe to 13.0 kOe. Finally, a comparative analysis between micromagnetic simulations and MFM images allowed us to determine the exchange stiffness (Aex) in the [Co60Fe40/Pt]5 multilayers.
关键词： exchange stiffness,femtosecond laser pulses,Landau-Lifshitz-Gilbert equation,[Co60Fe40/Pt]5 multilayers,damping,magnetic force microscopy,ultrafast magnetization dynamics,perpendicular magnetic anisotropy
更新于2025-09-12 10:27:22
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Nanomachining-enabled strain manipulation of magnetic anisotropy in the free-standing GaMnAs nanostructures
摘要： Strain perturbs atomic ordering in solids, with far-reaching consequences from an increased carrier mobility to localization in Si, stabilization of electric dipoles and nanomechanical transistor action in oxides, to the manipulation of spins without applying magnetic fields in n-GaAs. In GaMnAs, a carrier-mediated ferromagnetic semiconductor, relativistic spin-orbit interactions – highly strain-dependent magnetic interactions – play a crucial role in determining the magnetic anisotropy (MA) and anisotropic magnetoresistance (AMR). Strain modifies the MA and AMR in a nanomachined GaMnAs structure as measured by the anomalous Hall effect (AHE) and the planar Hall effect (PHE). Here, we report an MA modification by strain relaxation in an isolated GaMnAs Hall bar structure and by applying a range of local strains via fabricating asymmetrically mechanically buckled GaMnAs micro-Hall bar structures. in the AHe and pHe measurements, we observe a reduction in the in-plane MA and an enhancement in the out-of-plane MA as the compressive strain due to the lattice mismatch relaxes in the suspended structure. The functionality of such mechanical manipulation, as well as the two-level mechanical state and the corresponding AHe responses, is demonstrated by a fully scalable binary mechanical memory element in a GaMnAs single Hall cross structure.
关键词： strain,GaMnAs,magnetic anisotropy,planar Hall effect,anomalous Hall effect
更新于2025-09-12 10:27:22
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Magnetization reversal in NiFe <sub/>2</sub> O4/SrTiO <sub/>3</sub> nanoheterostructures grown by laser molecular beam epitaxy
摘要： NiFe2O4/SrTiO3(001) nanoheterostructures have been fabricated by laser molecular beam epitaxy method. Surface morphology and crystal structure of Ni-ferrite films were analysed by atomic force microscopy (AFM), reflection of high energy electron diffraction (RHEED), X-ray diffraction (XRD). X-ray methods prove the presence of inverse spinel crystal structure of films that was confirmed by measurements of spectral dependence of optical polar Kerr (PMOKE) effect. Study of magnetization reversal for different orientations of magnetic field carried out by vibration sample magnetometry (VSM) and longitudinal magneto-optical Kerr effect (LMOKE) are presented. In-plane magnetization loops exhibit 90 period indicating presence of biaxial magnetic anisotropy. Asymmetry of LMOKE hysteresis loops is related to manifestation of quadratic in magnetization effects in reflection of light.
关键词： nanoheterostructures,NiFe2O4/SrTiO3,biaxial magnetic anisotropy,laser molecular beam epitaxy,magnetization reversal
更新于2025-09-12 10:27:22
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Transparent Collision Visualization of Point Clouds Acquired by Laser Scanning
摘要： Exploring two-dimensional (2D) materials with room-temperature ferromagnetism and large perpendicular magnetic anisotropy is highly desirable but challenging. Here, through first-principles calculations, we propose a viable strategy to achieve such materials based on transition metal (TM) embedded borophene nanosheets. Due to electron deficiency, the commonly existent hexagon boron vacancies in various borophene phases serve as intrinsic anchor points for electron-rich transition metals, which not only adsorb strongly upon the vacancies but also favor to be embedded into the vacancies, forming 2D planar hybrid nanosheets. The adsorption-to-embedding transition is feasible thermodynamically and kinetically, owing to its exothermic nature and relatively small kinetic barriers. After embedding, phase transition is further proposed to obtain diverse structures of TM embedded borophenes with versatile magnetic properties. Based on the example of χ3 phase borophene, several ferromagnetic TM embedded borophene nanosheets with high Curie temperature and large perpendicular magnetic anisotropy have been predicted.
关键词： transition metal embedded borophene nanosheets,first-principles calculations,perpendicular magnetic anisotropy,room-temperature ferromagnetism,two-dimensional materials
更新于2025-09-11 14:15:04