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Öğe Comparative Analysis of Structural and Magnetic Properties in Co/Cu and Co/W Multilayers(Springer Wien, 2024) Tokac, M.Gilbert damping in symmetric Cu/Co/Cu and asymmetric Cu/Co/W multilayers was studied as a function of Co thickness using FMR linewidth measurements. W-capped multilayers showed higher intrinsic damping across all thicknesses, due to strong SOC in W, which enhances spin-pumping, and MDL formation at the Co/W interface, increasing spin-flip scattering. The higher spin-mixing conductance in W-capped multilayers is linked to stronger SOC and enhanced orbital hybridization at the Co/W interface. X-ray diffraction revealed an fcc(111) phase in Co layers up to 4 nm thick, with thicker films showing a mix of fcc(111) and hcp(0001) textures. The Co thin films showed saturation magnetizations near literature values. No dead layer was found in Cu-capped multilayers, however, a 0.3 nm MDL formed in W-capped multilayers due to atomic intermixing at the Co/W interface. FM/NM interfaces are crucial in generating and dissipating pure spin currents, and they significantly impact the damping properties through the influence of seed and capping layers.Öğe Gamma-ray shielding capability of CoFeTaB amorphous solids using Monte Carlo simulations and Phy-X/PSD software(Taylor & Francis Ltd, 2023) Tokac, M.; Khattari, Z. Y.; Al-Buriahi, M. S.Investigations on metallic glasses have increased significantly due to their obvious qualities such as high glass-forming ability, corrosion resistance, and chemical, mechanical, and magnetic properties. By considering the importance of Cobalt- and Iron-based metallic glasses with various Tantalum concentrations, a Monte Carlo simulation (Geant4 code) and Phy-X/PSD software were used to investigate their gamma-ray attenuation properties, such as mass attenuation coefficient, effective atomic number, and half-value layer for different photon energy ranges. The mass attenuation coefficient (MAC) was calculated numerically using the Phy-X/PSD software between 0.015 and 15 MeV, and the results were compared to Monte Carlo simulations. The mass attenuation coefficients of the alloys were ranged between 108.6 and 94.3 cm(2)/g for lowest the photon energy, while reduced to 0.0458 cm(2)/g at the high energy region. These results showed that the radiation protection effectiveness values may be correlated with the alloys' magnetization. The obtained results revealed that Tantalum density and larger atomic numbers are the most important factors in improving the radiation attenuation capabilities and then the shielding performance of the investigated glassy alloys.Öğe Influence of Ge concentration on magnetic properties of Co(1-x)Gex thin films(Springer Wien, 2024) Tokac, M.; Piskin, H.; Ozkal, B.; Aktas, K. Yildiz; Kocaman, B.; Arslan, L. colakerol; Rameev, B.Cobalt-rich Co(1-x) alloy thin films with various Ge concentrations (up to x=0.09) have been investigated by vibrating sample magnetometry and ferromagnetic resonance techniques to understand the influence of Ge doping on magnetostatic and magnetodynamic properties. Room-temperature magnetization curves have shown that the addition of Ge atoms can reduce the saturation magnetization in a fast manner. Utilizing a conventional ferromagnetic resonance setup, the out-of-plane angular dependencies of the resonance spectra have been measured and data have been analyzed using a computer program to simulate the magnetic behavior of the thin-film alloys. The experimental findings demonstrate that the magnetic properties of Co(1-x)Ge-x alloys can be precisely adjusted by varying the Ge content. Both the g-factor and the Gilbert-damping parameter show correlated changes, highlighting the tunability of these magnetic characteristics. This ability to modify saturation magnetization and damping parameters by altering the Ge concentration enables the optimization and customization of the alloy for specific applications in spintronic devices.Öğe Influence of tantalum concentrations on the magnetic properties of amorphous CoFeTaB thin-films(Elsevier, 2021) Tokac, M.The structural and magnetic properties of amorphous CoFeTaB thin-films were studied as a function of tantalum concentration. The investigations of the structural properties of amorphous CoFeTaB thin-films were undertaken to confirm layer thickness, interface roughness, and their amorphous structure. Temperature dependent magnetic characterizations were performed in order to extract Curie temperatures and their saturation magnetizations of each structure. Curie temperatures and saturation magnetizations of amorphous CoFeTaB thin-films show similar behaviour, where both quantities decrease with increasing tantalum concentration in thin-film structures. These reductions can be attributed to a result of a transfer of electrons from the metalloid atoms to the unfilled d holes of the 3d transition metals, and diffusion of tantalum atoms towards the ferromagnetic layer during thin-film deposition. Investigation of tuning both Curie temperature and magnetization by the addition of a non-magnetic transition metal is crucial for the development of spintronic applications.Öğe Spin orbit torque driven magnetization reversal in CoFeTaB/Pt probed by resonant x-ray reflectivity(Amer Physical Soc, 2022) Burn, D. M.; Fan, R.; Inyang, O.; Tokac, M.; Bouchenoire, L.; Hindmarch, A. T.; Steadman, P.Resonant soft-x-ray reflectivity and vibrating sample magnetometry have been used to characterize field driven and spin orbit torque driven magnetization reversal in a CoFeTaB/Pt bilayer. Reversal of the magnetization occurs either along the applied field direction or perpendicular to the current flow direction. Magnetometry results show that field driven (current driven) coercivities are reduced by application of a current (field) highlighting the roles played by the two external parameters. In the current switching case, it is demonstrated with soft-x-ray hysteresis loops that only the layers near the interface with Pt switch, possibly highlighting the role of proximity effects of the magnetized Pt. We show how magnetization reversal perpendicular to the beam results in hysteresis behavior in the reflected intensity that is dependent on the magnetization but independent of the helicity of the circular polarization of the incident beam.Öğe The role of W seed and spacer layers on the magnetic properties of Co/Pt multilayers(Elsevier, 2025) Tokac, M.; Piskin, H.; Ekinci, G.; Ozkal, B.; Kazan, S.The selection of seed and spacer layers is critical in influencing the magnetic properties of thin films, where these layers impact the microstructure, interface quality, and overall magnetic behavior of the thin films. The magnetic properties of Co/Pt multilayers have been investigated where the choice of seed and spacer layers is crucial for tailoring their magnetic properties. These layers influence the interfacial structure, and electronic environment, all of which contribute to variations in the effective demagnetizing field, g-factor, saturation magnetization, and perpendicular surface anisotropy constants. Ferromagnetic resonance has been used to investigate the enhancement of the Gilbert damping parameter, where the damping parameter is higher for the Cu/Co/Pt multilayers across the entire Co thickness range. In contrast, the presence of W layers on both sides of the Co layer leads to a reduction in the damping parameter. The higher spin-mixing conductance in the Co/Pt structure is linked to stronger SOC and enhanced orbital hybridization at the Co/Pt interface. As a consequence of their effects on spin-orbit interactions, spin-pumping efficiency, and interfacial quality, our results emphasize the critical role that interface characteristics play in improving damping in Co/Pt systems.Öğe Two Magnon Scattering Contribution to the Ferromagnetic Resonance Linewidth of Pt(Ir)/CoFeTaB/Ir(Pt) Thin Films(Springer Wien, 2023) Tokac, M.; Kazan, S.; Ozkal, B.; Al-jawfi, N.; Rameev, B.; Nicholson, B.; Hindmarch, A. T.The magnetic properties of Pt/CoFeTaB/Ir and Ir/CoFeTaB/Pt trilayer thin films have been studied using angular- and temperature-dependent ferromagnetic resonance. This enables quantitative determination of the various contributions to the magnetic behavior, including separating, the effective Gilbert damping, inhomogeneous damping, and two-magnon-scattering contributions to the magnetic dissipation. As-deposited films show behavior consistent with significant incorporation of Ir into CoFeTaB only when the Ir layer is deposited first. Annealing of the structures at 300 circle C\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$300\,<^>{\circ } \hbox {C}$$\end{document} causes only minor structural and magnetic modification when Pt is deposited first, and more pronounced changes, attributed to thermally-driven out-diffusion of Ir from CoFeTaB, are found when Ir is deposited first. A holistic consideration of the magnetic resonance behavior can provide detailed information on the atomic-scale structure in magnetic thin-film devices.
