Yazar "Cengiz, N. E." seçeneğine göre listele

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    Influence of Ti substitution on magnetic and magnetocaloric properties of Pr2Fe17-xTix intermetallic compounds
    (Springer, 2023) Cengiz, N. E.; Pektas, M.; Kaya, A. O.; Bayri, N.; Izgi, T.; Gencer, H.; Kolat, V. S.
    The structural, magnetic, and magnetocaloric properties of the Pr2Fe17-xTix (x = 0, 0.2, 0.4, 0.6) intermetallic compounds prepared by the arc-melting process were investigated. X-ray analyses indicated that all samples are single phase with the rhombohedral Th2Zn17-type structure. The unit-cell volume was determined to increase with the increasing Ti content. The magnetic measurements revealed that the Curie temperature increases with Ti content from 286 K for x = 0 to 337 K for x = 0.6. The maximum value of |Delta Sm| tends to decrease from 5.63 J/kg.K for x = 0 to 4.28 J/kg.K for x = 0.6 with increasing Ti content at 5 T magnetic field change. At the same magnetic field change, the relative cooling power (RCP) ranges from 425.17 J/Kg for x = 0 to 385.62 J/Kg for x = 0.6. The critical exponents (beta, gamma, and delta) determined from magnetocaloric data for x < 0.2 belong to mean-field model with long-range ferromagnetic interaction. A small deviation in the critical exponents of gamma and delta for x > 0.4 samples was attributed to inhomogeneous magnetic state of the samples. From the phase analysis, it was concluded that all samples showed a second-order magnetic phase transition.
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    Magnetic and Magnetocaloric Properties of Pr2Fe17-xCux Intermetallic Compounds
    (Korean Magnetics Soc, 2021) Cengiz, N. E.; Pektas, M.; Kolat, V. S.; Izgi, T.; Gencer, H.; Bayri, N.; Atalay, S.
    In this study, Cu-doped intermetallic compounds with the chemical composition of Pr2Fe17-xCux, (x = 0, 0.1, 0.2) were prepared by the arc-melting process. SEM analysis revealed that the samples consist of irregularly shaped and strongly connected micron-scale particles range from 0.5 mu m to 4 mu m. EDX analysis showed that all the samples consist of a single phase. The magnetic measurements revealed that all the samples exhibit a ferromagnetic to the paramagnetic phase transition. The Curie temperature was determined to increase linearly with increasing Cu substitution from 286 K for x = 0 to 303 K for x = 0.2. The maximum value of magnetic entropy change vertical bar Delta S-m vertical bar was estimated from isothermal magnetization curves and it decreases with increasing Cu content from 5.63 J/kg.K for x = 0 to 4.21 J/kg.K for x = 0.2 at 5 T magnetic field change. At the same magnetic field change, the relative cooling power values range from 404.8 J/Kg for x = 0 to 248.3 J/Kg for x = 0.2. Arrott plots and Landau analyses revealed that all the samples show second-order magnetic phase transition.
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    Production of LaCaMnO3 Composite by Ball Milling
    (Polish Acad Sciences Inst Physics, 2014) Gencer, H.; Cengiz, N. E.; Kolat, V. S.; Izgi, T.; Atalay, S.
    La0.67Ca0.33MnO3 perovskite-type manganite was synthesized by high-energy ball milling raw oxides of La2O3 (purity 99.9%), CaCO3 (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 La0.67Ca0.33MnO3 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 vanes in a broad range from nanometer scale to a few pm. 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.