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    Effect of Ag-doping process into the yttrium iron garnet (Y3Fe5O12) thin films on the structural, magnetic and optical properties
    (Springer, 2024) Demiryurek, Nazan; Akyol, Mustafa; Karadag, Faruk; Ekicibil, Ahmet
    In this work, the effect of Ag doping process (directly and as a nanoparticle) into the Y3Fe5O12 (YIG) thin films on the structural, morphological, optical and magnetic properties was studied in detail. Ag-doped YIG thin films were grown on thermally oxidized Si substrates by following sol-gel and spin-coating methods. All films were crystallized without cracks by two-stages heat treatment process. The XRD patterns confirm the formation of YIG peaks, and metallic Ag peaks which settled into the structure without bonding with the YIG components. In both Ag doping processes, the coercive field (H-c) and saturation magnetization (M-s) values of the samples containing 3% Ag are significantly lower than the other samples. The M-s values of 5% Ag doped samples were found the highest in both series. The M-s values of the films between in-plane and out-of-plane measurement increased with the Ag concentration. The optical measurements indicate an absorption peak in the range of 0-4 eV in both sample series and the optical band gap of the films decreased with the Ag doping due to its metallic characteristic. The ferromagnetic resonance measurements indicate that the lowest FMR linewidth as 92 Oe is seen in the 1% Ag-doped YIG sample. The relatively cheap and easy production of the used method and additive material may enable the widespread the usage of Ag-doped YIG thin films in magneto-optical devices.
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    Strong magnetic coupling in MnO? nanoparticles by doping Boron
    (Elsevier, 2021) Demiryurek, Nazan; Kivrak, Burak; Akyol, Mustafa; Ekicibil, Ahmet
    In this study, the effects of boron (B) doping into MnO delta were examined on structural and magnetic properties. The B-doped MnO delta MNPs were synthesized by polyol method at various B concentration changed from 0 to 15% by 5% steps. Majority MnO and a very weak Mn3O4 crystal diffraction were detected from x-ray diffraction experiments in undoped sample. In contrast to undoped sample, MnO peaks are disappeared and Mn3O4 becomes majority phase when B is doped into the main matrix, as well as observing new crystal orientation called B2Mn3O6. The crystallite size of Mn3O4 phase in undoped sample was calculated to be 62.4 nm. This value nonlinearly decreased to 33.3 nm by amount of B. From scanning electron microscopy images, the particle sizes of the synthesized nanoparticles were determined to be 5.01, 6.77, 6.23 and 7.51 nm for x = 0.0, 5.0, 10.0 and 15.0% in B-x:MnO delta, respectively. The magnetic hysteresis curves indicated that all samples exhibited ferromagnetic (paramagnetic) behavior at 5 K (room temperature). Interestingly, we observed a giant increment in the saturation magnetization (Ms) with boron content. The blocking temperature values obtained from M-T graphs were found to be 24.39, 42.03, 42.14 and 41.91 K for x = 0.0, 5.0, 10.0 and 15.0% in B-x:MnO delta, respectively. (c) 2020 Elsevier B.V. All rights reserved.
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    Structural, magnetic and optical properties of Au/YIG, YIG/Au and Au/YIG/Au multilayer thin film stacks
    (Elsevier, 2020) Akyol, Mustafa; Demiryurek, Nazan; Iloglu, Onur; Tumen, Kutluhan Utku; Karadag, Faruk; Ekicibil, Ahmet
    Y3Fe5O12 shortly named YIG thin film and various form of Au and YIG thin film stacks have been grown on quartz substrate using both spin-coating and sputtering methods. The films are crystallized in cubic phase after heat treatments process that is optimized to avoid cracks on the surface. The thickness of the YIG layer measured by cross-section electron microscope imaging technique are found as about 80 nm for all samples. While the root-mean-square surface roughness of the YIG film is in sub-nanometer scale, it increases up to 2.86 nm by adding Au layer in the film structure. All films exhibit in-plane easy axis and low coercive field at room temperature. But, the saturation magnetization values of films decrease with Au layer. Whereas the optical transmission value is around 80% for YIG samples above 400 nm, it decreases dramatically with Au in the film stacks. The highest absorption coefficient value is found as similar to 20 x 10(4) cm(-1) in Q/Au/YIG structure. This strong absorption might come from the localized surface plasmon polaritons of Au noble metals in YIG structure because it enhances the electronic transition from crystal field splitting. As a result of these measurements, it is seen that the Au layer reduces the magnetization of the films, while increases the absorption rate significantly. Due to considerably low production cost of YIG in this work, it might open to commonly use of them in the magneto-optical devices.