Browsing by Author "Kurt, M. S."

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Atomic Structures and Magnetic Moments in Cu1-xAgx Alloy Matrix-Embedded Fe Nanoparticle Systems
(Springer, 2022) Kurt, M. S.
Changes in magnetism were investigated through control over the atomic structure for Cu1-xAgx alloy matrix-embedded Fe nanoparticles systems. Nanocomposite magnetic films were prepared using the low-energy cluster beam deposition (LECBD) technique under ultra-high vacuum (UHV) conditions. Fe nanoparticles were produced by gas aggregation source, while alloy matrices were produced by MBE sources. Extended x-ray absorption fine structure (EXAFS) experiments revealed that the Fe nanoparticles in pure Cu have fcc structure while retaining their bulk bcc structure in Cu1-xAgx alloy matrix. Also, a slight decrease in Fe-Fe interatomic distances was observed in the bcc Fe structure due to the compression in the alloy matrix. The magnetic moment of Fe was initially very low because of its fcc structure in the pure Cu matrix, however, increased ultimately to values of similar to 2.7 mu(B)/atom with increasing Ag content in the alloy matrix.
Magnetic and Structural Changes in Cu1-Xalx Alloy Matrix - Embedded Fe Nanoparticle Systems
(Elsevier Science BV, 2019) Kurt, M. S.; Baker, S. H.; Roy, M.; Lees, M. R.
We describe the atomic structure and magnetism in Fe nanoparticles (similar to 2 nm) ebedded in a Cu1-xAlx alloy matrix. Nanocomposite films for these studies were prepared directly from gas phase using a flexible co-deposition technique under Ultra-High Vacuum (UHV) conditions. Fe nanoparticles and the alloy matrix were prepared using a gas aggregation source and MBE sources respectively. Extended x-ray absorption fine structure (EXAFS) experiments indicate that the embedded Fe nanoparticles retain a bcc structure for Al-contents greater than x = 0.13 but, for Al-contents lower than this value, Fe nanoparticles have both fcc and bcc structures. The magnetic moment per Fe atom initially increases with increasing Al-content due to the bcc structure becoming more dominant in the embedded nanoparticles as the Al-content is increased, but then decreases with further increase in Al-content. This decrease is consistent with a modest degree of alloying between Fe and Al atoms at the particle/matrix interfaces.
Magnetism and Structure in Nanocomposite Fe Nanoparticle/Al Matrix Films
(Elsevier Science Sa, 2019) Kurt, M. S.; Baker, S. H.; Roy, M.; Lees, M. R.
We describe magnetometry measurements performed on nanocomposite films formed of Fe nanoparticles embedded in Al matrix. The samples were prepared using a flexible co-deposition technique under Ultra-High Vacuum (UHV) environments. Fe nanoparticles, made by using a gas aggregation source, were co-deposited with an atomic Al beam, made by an MBE source. The Volume Filling Fraction (VFF) of nanoparticles was varied controllably between 4% and 45%, while the mean diameter of Fe nanoparticles produced by the source was similar to 2 nm. Fe K edge extended x-ray absorption fine structure (EXAFS) experiments show that there is a high degree of alloying between Fe nanoparticles and Al atoms. Magnetism in the embedded Fe nanoparticle samples was investigated using a SQUID magnetometer. Atomic moment of Fe in the Fe/Al nanocomposite films increases slightly when the proportion of Fe nanoparticles is increased, but is still significantly lower than the bulk Fe value. In a more detailed analysis, the magnetisation curves were fitted using the Random Anisotropy Model (RAM) which allowed the exchange field and random anisotropy field to be evaluated. The findings and issues raised by this approach are discussed. (C) 2019 Elsevier B.V. All rights reserved.
Silicon-Doping Influence on the Crystalline, Surface and Optical Features of Cadmium Oxide Films Deposited by Sol-Gel Spin Route
(Elsevier GmbH, 2018) Turgut, G.; Kurt, M. S.; Ertugrul, M.; Iskenderoglu, D.; Duman, S.; Gurbulak, B.
This is the first study on Si-contributed CdO films fabricated via sol-gel process. Si-doping impact on the crystalline, topographic and optical qualities of cadmium oxide has been searched with XRD, SEM, AFM and UV/vis spectrophotometer. The whole films were polycrystalline with (111) preferential direction and the crystalline degree of CdO depended on Si-contribution effect. The crystallite size of undoped-CdO incessantly decreased with Si-content, however dislocation density increased with Si-level. The spherical CdO granules were nanoscale and their sizes varied between 20-170 nm. The RMS roughness values of films changed between 5.84 nm-40.5 nm. The optical gap value of undoped-CdO continuously declined from 2.59 eV to 2.39 eV with increasing Si-content, while the Urbach energy increased from 350 meV to 468 meV with Si-level. These results reveal that the level of Si-doping affect the features of cadmium oxide. (C) 2018 Elsevier GmbH. All rights reserved.