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1
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Field Induced Unusual Magnetic Behavior at Low Temperature in Pr_{0.67}Ca_{0.33}MnO_3

100%
Pektas M., Gencer H., Izgi T., Kolat V., Atalay S.
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vol. 125
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issue 2
217-219
EN
In this study, magnetic properties of Pr_{0.67}Ca_{0.33}MnO_3 compound were investigated in detail. The magnetization versus temperature (M-T) curve showed that this material undergoes a charge order transition at 200 K. A more pronounced FM phase appeared below 56 K. At T = 5 K, a field induced sharp step like magnetisation transition associated with phase separation was observed. However, after application of 7 T magnetic field at 5 K, the magnetic behaviour of sample was changed completely and full FM behaviour was observed. The more interesting is that the sample remains in the FM state and does not retrieve the initial magnetic state until warmed up to charge order transition temperature. Large negative magnetic entropy change (- 26.18 J/(kg K) at 38 K and 5 T) was attributed to step like magnetisation transition.
2
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Production of LaCaMnO_3 Composite by Ball Milling

100%
Gencer H., Cengiz N., Kolat V., Izgi T., Atalay S.
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vol. 125
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issue 2
214-216
EN
La_{0.67}Ca_{0.33}MnO_3 perovskite-type manganite was synthesized by high-energy ball milling raw oxides of La_2O_3 (purity 99.9%), CaCO_3 (purity > 99%), and MnO (purity > 99%). The ratio of ball and powder weight was 10:1 and the rotating speed was set to 500 rpm. X-ray analysis indicated that La_{0.67}Ca_{0.33}MnO_3 single phase was formed completely when milling time is up to 4 h. The peak intensity of perovskite structure decreased and a hump-like peak appeared with further milling time. When the milling time is longer than 40 h, the perovskite structure disappeared and the amorphous phase was formed completely. Scanning electron microscopy picture of 24 h milled sample showed that the particle size generally varies in a broad range from nanometer scale to a few μm. The magnetic measurements showed that ball milling samples have an inhomogeneous magnetic state and exhibit spin-glass like behavior. The significantly small magnetic entropy change and a remarkably broad temperature interval in entropy change were attributed to high degree of structural and magnetic disorder and broadening of magnetic transition.
3
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Magnetoresistance of Electrochemically Produced NiFe and CoNiFe Nanowires

100%
Avcu D., Atalay F., Aydogmus E., Kaya H., Atalay S.
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vol. 125
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issue 2
230-231
EN
CoNiFe and NiFe nanowires were electrochemically produced by dc electrodeposition on highly ordered porous anodic alumina oxide templates. Scanning electron microscope images of nanowires after removing the alumina membrane showed that these nanowires are uniform with the diameters of about 220-300 nm and about 25-30 μm length. The energy dispersive X-ray analysis showed that the composition of the nanowires is Ni_{88}Fe_{12}, Co_7Ni_{82}Fe_{11}. Magnetic field was applied by an electromagnet and resistance was measured by four point technique.
4
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Crack Detection Using Fluxgate Magnetic Field Sensor

100%
Izgi T., Goktepe M., Bayri N., Kolat V., Atalay S.
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vol. 125
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issue 2
211-213
EN
In this study, the variation of the magnetic flux distribution in a magnetised ferromagnetic material which has in homogeneity as a crack is studied. An orthogonal fluxgate magnetic field sensor was used in the inspection of cracks. In the fluxgate sensor, the sensing element (Co_{0.94}Fe_{0.06})_{72.5}Si_{12.5}B_{15} amorphous ferromagnetic wire was placed inside a pickup coil winding with 50 μm copper wire and connected to a signal generator and the output from pick-up coil was detected using a lock-in amplifier. The surface profile of magnetic materials with a crack was obtained using a specially designed 3-dimensional moving system. A large decrease in the output voltage of the sensor was observed when the sensor was moved on the top of the crack, after the further movement of the sensor the output voltage came back to the previous value.
5
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Magnetoimpedance Effects in Electrodeposited NiFe Nanowire Array

100%
Aydogmus E., Kaya H., Atalay F., Atalay S., Avcu D.
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vol. 125
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issue 2
227-229
EN
In this work, NiFe nanowires were grown in highly ordered porous anodic alumina oxide templates by dc electrodeposition at a pH value of 2.6. Scanning electron microscopy showed that wires have diameters of about 250-310 nm and length 25-30 μm. The energy dispersive X-ray analysis showed that the composition of the nanowires is Ni_{65}Fe_{35}. Electrical contacts were made on both sides of the nanowire array and their magnetoimpedance properties were investigated. All the magnetoimpedance curves showed single peak behavior due to the high shape anisotropy. The maximum magnetoimpedance change at the 79 MHz driving current frequency was ≈ 1.45%.
6
Content available remote

Magnetoresistance of Electrodeposited Co/Cu Multilayer Nanowires

100%
Avcu D., Atalay F., Atalay S., Kaya H., Aydogmus E.
Acta Physica Polonica A
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2015
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vol. 127
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issue 4
1115-1117
EN
Co/Cu multilayer nanowires were electrodeposited potentiostatically on highly ordered porous anodic alumina oxide templates. Scanning electron microscopy (SEM) showed that wires have diameters of about 250-300 nm and length of 40-50 μm. Co/Cu multilayer nanowire arrays embedded in anodic alumina oxide were mechanically polished with diamond in a suspension of oil until the wires appeared. Then the top and bottom surfaces of the material were coated with a layer of Au with a thickness of 100 nm for electrical contacts. Magnetic field was applied by an electromagnet and resistance was measured by four point technique.
7
Content available remote

Production of Y-Ba-Cu-O Nanowires and Nanotubes by Electrochemical Method

100%
Kaya H., Atalay F., Avsar D., Yagmur V., Atalay S.
Acta Physica Polonica A
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2013
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vol. 123
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issue 2
209-211
EN
In this work, the technological aspects of great importance YBa_2Cu_3O_{7-x} superconducting materials were produced in the form of nanotube by electrochemical method. The electrochemical deposition conditions for the Y-Ba-Cu deposition in nanoporous Al_2O_3 were investigated. The heat treatment was applied to Y-Ba-Cu/Al_2O_3 nanopatterns, to form superconductive phase. The resulting nanostructures were found to be in length 4-5 μm, 177-210 nm in diameter. The produced nanostructures at - 4 V and more positive potentials were Y-Ba-Cu nanowires, while the nanostructures deposited at the more negative potentials were of nanotube form.
8
Content available remote

YIG Film for Magnetic Field Sensor

86%
Kaya A., Atalay S., Gencer H., Kaya O., Kolat V., Izgi T.
Acta Physica Polonica A
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2015
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vol. 127
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issue 4
937-939
EN
Single crystal Y₃Fe₅O_{12} (YIG) film was grown onto (111) oriented gadolinium gallium garnet (GGG) substrate by the liquid phase epitaxy (PLD) technique. The X-ray diffraction measurements showed that epitaxial growth of the film along its (111) axis. The surface characteristic was investigated by atomic force microscopy (AFM) measurement. The magnetic field sensor consisted of a rectangular shape with 5 mm wide, 15 mm long and 5 μm thick YIG film and a pair of identical 50 μm wide microstrip copper transducers elements separated by 6 mm. The filter was tested by measuring reflection S_{11} characteristic at various bias magnetic fields. The results have showed that when the bias field increased from 0 to 2.5 kOe, the frequency value corresponding to S_{11} maxima increased from 1 GHz to 9 GHz. This suggests that the wide range magnetic field sensing and the highly sensitive field sensing are simultaneously fulfilled with the YIG film.
9
Content available remote

Crystallisation Kinetics of Co_{75-x}M_xSi_{15}B_{10} (M = Fe, Mn, Cr and x=0, 5) Amorphous Alloys

86%
Bayri N., Kolat V., Izgi T., Atalay S., Gencer H., Sovak P.
Acta Physica Polonica A
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2016
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vol. 129
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issue 1
84-87
EN
In this study, the effect of Fe, Mn and Cr substitution for Co on the crystallization kinetics of amorphous Co_{75-x}M_xSi_{15}B_{10} (M = Fe, Mn and Cr; x=0 and 5) alloys were investigated. The broad diffraction peaks in the X-ray diffraction patterns for as-quenched ribbons indicated that all of the samples exhibit an amorphous structure. The activation energies of the alloys were calculated from differential thermal analysis data using the Kissinger, Ozawa and Augis-Bennett models. The increased activation energy for Fe, Mn and Cr doped samples indicated that the thermal stability and the crystallization kinetics were improved in the doped samples. The value of the Avrami exponent indicated that the crystallization is typical diffusion controlled three-dimensional growth for all of the samples.
10
Content available remote

The Formation of Free Standing NiO Nanostructures on Nickel Foam for Supercapacitors

86%
Atalay F., Aydogmus E., Yigit H., Avcu D., Kaya H., Atalay S.
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vol. 125
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issue 2
224-226
EN
In this study, free standing NiO nanostructures for supercapacitors were obtained by means of chemically depositing of nickel oxide on Ni foam and then they were annealed at various temperatures. The morphological properties of densely covered Ni foams were studied by scanning electron microscopy. Supercapacitor characteristics, such as charging/discharging and impedance characteristics, were also examined.
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