Browsing by Author "Köçkar, Hakan"

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Effect of potantiostatic waveforms on properties of electrodeposited NiFe alloy films
(Springer, 2004-12) Köçkar, Hakan; Topcu, H.; Alper, Mürsel; Uludağ Üniversitesi/Fen-Edebiyat Fakültesi/Fizik Bölümü.; AAG-8795-2021; 7005719283
The influence of the deposition potentials applied in continuous and pulse waveforms on the properties of the electrodeposited NiFe alloy films have been investigated. The films were grown on (100) textured polycrystalline copper substrates. During growth, the films were characterized by recording the current-time transients. The composition of samples was determined by inductively coupled plasma atomic emission spectrometry (ICP-AES). The analysis results revealed that the Fe content in the films decreases as both the deposition potential and the film thickness increase. The X-ray patterns showed that the films have face centred cubic (fee) structure as their substrates and the (111) texture. The magnetic characteristics of films studied by a vibrating sample magnetometer (VSM) were found to vary depending on the type of the deposition (pulse or continuous) and the thickness of samples. The easy axis is in the film plane for all samples.
Properties of electrodeposited Co-Mn films: Influence of deposition parameters
(Elsevier, 2015-12-30) Karpuz, Ali; Köçkar, Hakan; Alper, Mürsel; Uludağ Üniversitesi/Fen Edebiyat Fakültesi/Fizik Bölümü.; AAG-8795-2021; 7005719283
Co-Mn films were produced with electrodeposition considering the deposition parameters of electrolyte pH value, Mn concentration of the electrolyte and film thickness. The effect of each parameter on the structural, magnetic and magnetoresistance properties of the films was studied, separately. X-ray diffraction measurement showed that the films have hexagonal close packed structure. For the films deposited at different pH values, the surface morphologies with different-sized globular granules were observed whereas the morphology covered by uniformly distributed nanoscale grains was detected for the surfaces of all films produced from electrolytes with different Mn concentrations. Also, the ribbed surfaces for 6 mu m and 4 mu m, and the nano-sized acicular surface morphologies for 2 mu m were observed. To the results of magnetic measurements, the saturation magnetization was found to be 1230 emu/cm(3) for all films deposited at different electrolyte pHs. The highest remanent magnetization value was obtained to be 882 emu/cm(3) for the film produced from the electrolyte containing 0.06 M Mn concentration. The coercivity, H-c, values decreased from 147 Oe to 43 Oe when the electrolyte pH decreased from 4.7 to 2.6. And, the Hc continued to decrease from 45 Oe to 31 Oe when the Mn concentration increased from 0.02 M to 0.06 M, and from 27 Oe to 22 Oe when the film thickness decreased from 6 pin to 2 mu m. It is seen that the Hc was immensely affected by the deposition parameters applied during the film production. The Co-Mn films with low Hc were achieved using relatively low electrolyte pH, high Mn concentration of electrolyte and low film thickness, respectively. Also, influence of the deposition parameters affect Hc is in order of the electrolyte pH, the Mn concentration in the electrolyte and the film thickness (from high to low influence). As it is observed that the magnetic properties are sensible to the deposition parameters and the Co-Mn films may have the potential applications in magnetic recording and sensors technologies.
Properties of electrodeposited CoFe/Cu multilayers: The effect of Cu layer thickness
(Elsevier, 2015-01-01) Şahin, Turgut; Köçkar, Hakan; Alper, Mürsel; Uludağ Üniversitesi/Fen-Edebiyat Fakültesi/Fizik Bölümü.; AAG-8795-2021; 7005719283
CoFe/Cu mulfflayers were potentiostatically electrodeposiled on Ti substrates as a function of different non-magnetic (Cu) layer thicknesses, and their characterizations were investigated. The compositional analysis performed by energy dispersive X-ray spectroscopy disclosed that the Cu content in the multilayers increased and the Co content decreased as non-magnetic layer was increased. However, the Fe content was almost stable. The scanning electron microscopy studies showed that the surface morphology of the films is strongly affected by the non-magnetic layer thickness, and X-ray diffraction was used to analyse the structural properties of the multilayers and revealed that the multilayers have face-centred cubic (fcc) structure and their preferred orientations change depending on the Cu layer thickness. In the case of magnetoresistance measurements of the multilayers performed at room temperature, the highest giant magnetoresistance (GMR) values exhibited for the films with the Cu layer thickness (6.0 nm) whereas the lowest GMR magnitudes were observed for the films without Cu layer. Therefore, the variations of the Cu layer thicknesses were observed to have a significant effect on the GMR of multilayers. The differences observed in the magnetotransport properties were attributed to the microstructural changes caused by the Cu layer thickness.
Role of electrolyte pH on structural and magnetic properties of Co-Fe films
(Elsevier, 2010-05) Köçkar, Hakan; Şahin, Turgut; Karaağaç, Öznur; Alper, Mürsel; Uludağ Üniversitesi/Fen-Edebiyat Fakültesi/Fizik Bölümü.; AAG-8795-2021; 7005719283
Co-Fe films were electrodeposited on polycrystalline Titanium substrates from the electrolytes with different pH levels. X-ray diffraction (XRD) was used to study the crystal structure of the films. The XRD patterns showed that the films grown at the pH levels of 3.70 and 3.30 have a mixed phase consisting of face-centred cubic (fcc) and body-centred cubic, while those grown at pH=2.90 have only fcc structure. It was observed that the film composition, by energy dispersive x-ray spectroscopy, contain around 88 at% Co and 12 at% Fe for all films investigated in this study. Morphological observations indicated that all films have grainy structure with the slight change of grain size depending on the electrolyte pH. Magnetoresistance measurements, made at room temperature, showed that all films exhibited anisotropic magnetoresistance, which is affected by the electrolyte pH. From the magnetic measurements made by vibrating sample magnetometer, the saturation magnetization increases as the electrolyte pH decreases. Furthermore, all films have in-plane easy-axis direction of magnetization.