Browsing by Author "Karpuz, Ali"

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Change in planar hall effect ratio of Ni-Co films produced by electrodeposition
(Elsevier, 2015-01-01) Karpuz, Ali; Koçkar, Hakan; Alper, Mürsel; ALPER, MÜRSEL; Uludağ Üniversitesi/Fen-Edebiyat Fakültesi/Fizik Bölümü.; AAG-8795-2021
Ni-Co Films were produced by the electrodeposition technique and their magnetotransport properties were studied. The anisotropic magnetoresistance (AMR) and the planar Hall effect (PRE) ratios were Found using the van der Pauw setup at room temperature. It was observed that the ORE ratios were larger than the obtained AMR ratios. While the maximum changes in longitudinal and transversal magnetoresistance ratios were 6.8% and 140%, respectively, the change in ORE values was up to 500%. In the ORE measurements, the magnetoresistance orientation depends on the electrical resistance values which occur in branches of the films.
The effect of different chemical compositions caused by the variation of deposition potential on properties of Ni-Co films
(Elsevier, 2011-02-01) Karpuz, Ali; Koçkar, Hakan; Alper, Mürsel; Uludağ Üniversitesi/Fen-Edebiyat Fakültesi/Fizik Anabilim Dalı.; AAG-8795-2021; 7005719283
The magnetic and microstructural properties of Ni-Co films electrodeposited at different cathode potentials were investigated. The compositional analysis revealed that the Ni content increases from 13 at.% to 44 at.% in the films with increasing deposition potential. Magnetic measurements showed that the saturation magnetization, M(s) of the films decreased with increase of Ni content as the deposition potential increased. Ms values changed between 1160 emu/cm(3) and 841 emu/cm(3). The X-ray diffraction revealed that the crystalline structure of the films is a mixture of the predominant face-centered cubic (fcc) and hexagonal closed packed. However, the mixture phase turns to the fcc because of increasing Ni content up to 44 at.% at the highest (-1.9 V) potential by enhancing the intensity of reflections from the fcc phase. The changes observed in the magnetic and microstructural properties were ascribed to the changes observed in the chemical composition caused by the applied different deposition potentials.
Effect of film thickness on properties of electrodeposited Ni-Co films
(Elsevier, 2012-04-01) Karpuz, Ali; Koçkar, Hakan; Alper, Mürsel; Uludağ Üniversitesi/Fen-Edebiyat Fakültesi/Fizik Bölümü.; AAG-8795-2021; 7005719283
A series of Ni-Co films with different thicknesses was produced by using the electrodeposition technique and their microstructural, magnetic and magnetotransport properties were investigated. The X-ray (XRD) diffraction measurements showed that the films have the face centered cubic structure and the preferential orientations of the films were in the order of (1 1 1), (2 2 0) and (2 2 0) for the films with 1, 2 and 4 mu m thicknesses, respectively. The magnetic measurements revealed that the coercivity decreased from 52 Oe to 37 Oe due to the regular transition of preferential orientation from (1 1 1) to (2 2 0) with increasing film thickness. The study demonstrated that magnetic properties of the films changed according to the microstructural properties. Magnetoresistance investigations exhibited that all films have anisotropic magnetoresistance (AMR).
Electrochemical production of Fe-Cu films: Determination of the deposition potentials and their effect on microstructural and magnetic properties
(Edp Sciences, 2009-12) Karpuz, Ali; Koçkar, Hakan; Alper, Mürsel; Uludağ Üniversitesi/Fen-Edebiyat Fakültesi/Fizik Bölümü.; AAG-8795-2021; 7005719283
Fe-Cu alloys were grown on polycrystalline titanium substrates after determining the suitable deposition potentials. Based on the results obtained from cyclic voltammetry curves, a potential region between -1.8 V and -2.3 V vs. saturated calomel electrode (SCE) was selected. During growth, the electro-chemical characterizations of the films were made by recording the current-time transients. The structure of films becomes more brittle with the increase of the deposition potential over -2.3 V vs. SCE due to extreme hydrogen liberation from cathode surface. The structural analysis by the X-ray diffraction demonstrated that the films have a typical body centered cubic of alpha-Fe preferentially grown in the (211) direction. The grain sizes, lattice parameters and interplanar spacings were also calculated. Energy dispersive X-ray spectroscopy measurements demonstrated that the ratio of Fe:Cu was almost the same. The magnetic analysis by vibrating sample magnetometer indicated that the coercivity of the films was slightly affected by the deposition potential.
Electrodeposited Co-Ni films: Electrolyte pH-property relationships
(Springer, 2013-03) Karpuz, Ali; Koçkar, Hakan; Alper, Mürsel; Uludağ Üniversitesi/Fen-Edebiyat Fakültesi/Fizik Anabilim Dalı.; AAG-8795-2021; 7005719283
The effect of electrolyte pH on structural, magnetic, and magnetoresistive properties of Co-Ni films was studied. The films were deposited on a titanium substrate from the electrolytes with 4.10 +/- 0.05, 3.14 +/- 0.05, and 2.14 +/- 0.05 pH values. The Co-Ni system exhibited anomalous codeposition. Structural analysis indicated that the films had (220) preferential oriented face-centered cubic structure and their surface became smoother as the electrolyte pH decreased. The compositional and magnetic analysis revealed that an increase of the Co content in the films resulted in an increase in saturation magnetization and coercivity. Magnetoresistance curves indicated that the films show anisotropic magnetoresistance. Longitudinal and transversal magnetoresistances were found to be the highest values of 8 % and 7 %, respectively, for the film deposited at a low electrolyte pH. The variation of the Co:Ni ratio in deposits caused by the change of the electrolyte pH has a considerable effect on the properties of the films.
Electrodeposited Ni-Co films from electrolytes with different Co contents
(Elsevier, 2012-02-01) Karpuz, Ali; Koçkar, Hakan; Karaağaç, Öznur; Alper, Mürsel; Hacıismailoğlu, Mürşide; Uludağ Üniversitesi/Fen-Edebiyat Fakültesi/Fizik Bölümü.; 0000-0001-5648-3230; AAG-8795-2021; AAH-9719-2021; 36482867500; 7005719283
The properties of electrodeposited Ni-Co films produced from electrolyte consisted of nickel sulfamate, cobalt sulfate and boric acid were investigated as a function of Co content in the films. The compositional analysis performed by an energy dispersive X-ray spectroscopy demonstrated that the Co content of the films increases as the cobalt sulfate concentration in the electrolyte increases. The anomalous codeposition behavior was observed for all concentrations. The crystal structure was analyzed using an X-ray diffraction technique. The face centered cubic (fcc) structure was observed in the films containing from 0 at.% Co to 58 at.% Co. For the higher atomic Co contents (64 at.% and 80 at.%), a mixed phase of dominantly fcc and hexagonal closed packed (hcp) structure was observed although the (10.0) and (10.1) hcp peaks had minor intensities in the patterns. Surface micrographs obtained from a scanning electron microscope revealed that the film surface has a rougher appearance as the Co content increases. Magnetic measurements showed that the saturation magnetization gradually increased with increasing Co content of the films. The coercivity, H-c can be controlled by the structural parameters such as average grain size and crystal structure. The results also indicated that the optimum film composition was 28-40 at.% Co since the lower H-c and higher magnetoresistance (MR) values with very smooth or slightly granular surfaces were achieved at this Co content. It is revealed that Co content has an important effect on structural, magnetic and MR properties of the Ni-Co films.
Microstructure dependence of magnetic properties on electrochemically produced ternary CuCoNi alloys
(Springer, 2014-07-18) Karpuz, Ali; Koçkar, Hakan; Alper, Mürsel; Uludağ Üniversitesi/Fen Edebiyat Fakültesi/Fizik Bölümü.; AAG-8795-2021; 7005719283
Ternary CuCoNi alloys were deposited by electrodeposition and the effect of different deposition potentials on the microstructural and magnetic properties of the alloys was investigated. The deposition potential was changed from -1.0 to -1.3 V versus saturated calomel electrode. Anomalous co-deposition occurred for all ternary alloys. All alloys have a face centered cubic (fcc) crystalline structure and the peaks of fcc Cu transformed to those of fcc Ni when the deposition potential was increased from -1.0 to -1.3 V, which was confirmed by the energy dispersive X-ray spectroscopy. The atomic Ni content of the ternary alloys increased from 8 to 33 % when the deposition potential was increased from -1.0 to -1.3 V. On the film surfaces, a specific growth orientation and micro-sticks gradually altered to spherical micro-grains when the deposition potential was increased. Saturation magnetization, M-s and coercivity, H-c of the alloys were significantly affected by different deposition potentials. The M-s value varied between 308 and 674 emu/cm(3) when the deposition potential was changed from -1.0 to -1.3 V. And, the H-c gradually decreased from 169 Oe to 112 Oe when the potential increased from -1.0 to -1.3 V. The changes in the magnetic properties of the alloys are related with the variations in the microstructural properties caused by deposition potential. Besides, the anisotropic magnetoresistance magnitudes were found to depend on the deposition potential.
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.
The role of Cu content on properties of electrodeposited Fe-Cu films
(Amer Scientific Publishers, 2009-06) Karpuz, Ali; Koçkar, Hakan; Alper, Mürsel; Uludağ Üniversitesi/Fen-Edebiyat Fakültesi/Fizik Bölümü.; AAG-8795-2021; 7005719283
The microstructural and magnetic properties of Fe-Cu films were studied in terms of Cu content in the films. The results of energy dispersive X-ray spectroscopy showed that the Cu content in the films increases as the Cu concentration in the electrolyte is increased. The increase of the Cu content in the films makes the film morphology seem cauliflower-like structure and the films with Cu have rougher surface than pure Fe films. The X-ray diffraction revealed that the films have body-centered cubic structure of alpha-Fe, and the Fe film has the (100) preferential texture whereas the Fe-Cu film containing 9.5 wt% Cu has the (110) preferential texture. The magnetic analysis carried out by vibrating sample magnetometer showed that the increase of the Cu content in the film results in the decrease of the saturation magnetization and the increase of the coercivity, and the easy-axis direction of the magnetization is parallel to the film plane. It is seen that the microstructural and magnetic properties of the Fe-Cu films changes depending on the film content.
Scanning of nickel sulfamate concentration in electrodeposition bath used for production of Ni-Co alloys
(Springer, 2013-09) Karpuz, Ali; Koçkar, Hakan; Alper, Mürsel; Uludağ Üniversitesi/Fen-Edebiyat Fakültesi/Fizik Bölümü.; AAG-8795-2021; 7005719283
The Ni-Co films were produced by using the electrodeposition technique from the electrolytes with different Ni(SO3 center dot NH2)(2)center dot 4H(2)O concentrations (from 0 to 0.45 M). The Ni content of the films changed gradually from 0 to 57 %. The Ni-Co system exhibited anomalous codeposition. For 0 at.% Ni content, the saturation magnetization, M-s of the film was found to be 1298 emu/cm(3), which is close to that of bulk Co (1420 emu/cm(3)). As the Ni content increased, M-s decreased since the M-s value of bulk Ni (480 emu/cm(3)) is lower than that of bulk Co. The coercivity, H-c, of Co film was found as 37 Oe. When the Ni content increased to 6 at.%, the H-c value dramatically increased to 109 Oe. The hexagonal closed packed (hcp) structure was observed for the films containing 0 and 6 at.% Ni. When the Ni content increased to 25 at.%, a mixed phase of face centered cubic (fcc) and hcp structure (mostly fcc) was detected. For further increase in Ni content (39 and 57 at.%), the peaks which occurred from the reflections of fcc phase were obtained. As a result of structural analysis, the Co content can be determined as 62-64 at.% for changing of crystal structure. The transfiguration from spherical granular to acicular surface morphology occurred around 75 at.% Co content. Magnetoresistance of the films was measured and it was found that the films show anisotropic magnetoresistance.
Study of electrolyte pH in production of Cu-Co-Ni ternary alloys and its effect on microstructural and magnetic properties
(IEEE-Inst Electrical Electronics Engineers Inc, 2014-05-20) Karpuz, Ali; Koçkar, Hakan; Alper, Mürsel; Uludağ Üniversitesi/Fen Edebiyat Fakültesi/Fizik Bölümü.; AAG-8795-2021; 7005719283
Cu-Co-Ni alloys were electrodeposited in the mediums that have different pH levels to investigate the microstructure-magnetic relationship. The electrolyte pH was considered as high (4.2) and low (2.5) levels. For both levels, the anomalous codeposition occurred in the deposition of the alloys. The face centered cubic crystalline structure was observed in the ternary alloys grown at high and low electrolyte pH levels. In addition, a significant decrease in average grain size of the crystallites, from 60 to 21 nm, occurred when the pH was reduced from 4.2 to 2.5. A dendritic structure was detected in the surface of the alloy deposited from electrolyte with the high pH level, whereas the alloy grown at the low pH has a surface without dendritic clumps. According to magnetic analysis, an increase in the saturation magnetization, caused by the increase of Co content, was detected when the pH was reduced. The coercivity H-c levels were 89 and 80 Oe for the alloys grown at high and low pH, respectively. The change of H-c was attributed to the changes in microstructural properties, i.e., different average grain sizes of the crystallites and surface morphologies, occurred when the electrolyte pH changed. The anisotropic magnetoresistance (AMR) was exhibited by the alloys and the AMR ratio was enhanced from similar to 3% to similar to 3.5%-4% when the pH decreased.
Substrate type and their rotation speed controlled magnetic anisotropy of iron films evaporated by a newly designed vacuum coating system
(Natl Inst Optoelectronics, 2014-03) Kockar, Hakan; Karaağaç, Öznur; Kuru, Hilal; Karpuz, Ali; Hacıismailoğlu, Mürşide S.; Alper, Mürsel; Akkaya, Cengiz; Uludağ Üniversitesi/Fen Edebiyat Fakültesi/Fizik Bölümü.; AAH-9719-2021; AAG-8795-2021; 36482867500; 7005719283; 14061855100
A newly designed Vacuum Coating System (VCS) system has been used for the first time to prepare magnetic iron thin films on plastic kapton and rigid glass substrates at different rotation speeds (0 rpm, 30 rpm, 60 rpm, and 90 rpm). The powdered iron as a source material was evaporated by a resistively heated furnace positioned right under the substrate within the VCS system. Magnetic measurements showed that an in-plane magnetic anisotropy exist in all films. The films deposited on flexible kapton show that the degree of uniaxial magnetic anisotropy and coercivity decreased with decreasing rotational speed. For glass substrates used at low speeds (0 rpm and 50 rpm) magnetic isotropy was observed and coercivity was found to be almost constant while a slight anisotropy and a small change of coercivity was observed at 90 rpm. Coercivity of the films deposited on kapton substrates was found to be higher than that of the films on glass substrates. The estimation of in-plane uniaxial anisotropy was obtained from the hysteresis loops of the films confirmed the experimental in-plane magnetic anisotropy findings. Observations indicate that the uniaxial in-plane magnetic anisotropy and coercivity are dependent on the type of substrate and their rotation speeds.