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    Crystallization kinetics of Fe73.5-xMnxCu1Nb3Si13.5B9 (x=0, 1, 3, 5, 7) amorphous alloys
    (Elsevier Science Bv, 2009) Bayri, N.; Izgi, T.; Gencer, H.; Sovak, P.; Gunes, M.; Atalay, S.
    In this study, we have investigated the effect of substituting Mn for Fe on the crystallization kinetics of amorphous Fe73.5-xMnxCu1Nb3Si13.5B9 (x = 1, 3, 5, 7) alloys. The samples were annealed at 550 degrees C and 600 degrees C for 1 h under an argon atmosphere. The X-ray diffraction analyses showed only a crystalline peak belonging to the alpha-Fe(Si) phase, with the grain size ranging from 12.2 nm for x = 0 to 16.7 nm for x = 7. The activation energies of the alloys were calculated using Kissinger, Ozawa and Augis-Bennett models based on differential thermal analysis data. The Avrami exponent n was calculated from the Johnson-Mehl-Avrami equation. The activation energy increased up to x = 3. then decreased with increasing Mn content. The values of the Avrami exponent showed that the crystallization is typical diffusion-controlled three-dimensional growth at a constant nucleation rate. (C) 2008 Elsevier B.V. All rights reserved.
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    Electrical transport and magnetoresistance properties of La0.67Ca0.33Mno3 film coated on pyrex glass substrate
    (World Scientific Publ Co Pte Ltd, 2008) Gencer, H.; Goktas, A.; Gunes, M.; Mutlu, H. I.; Atalay, S.
    The electrical transport and magnetoresistance properties of the polycrystalline La0.67Ca0.33MnO3 film produced on a Pyrex substrate were investigated for the first time. X-ray powder diffraction indicated that the film sample has a perovskite structure. Scanning electron microscope indicated that La0.67Ca0.33MnO3 film thickness is approximately 500 nm, and the average grain size of this sample varies between 40 and 50 nm. La0.67Ca0.33MnO3 film showed a phase transition from paramagnetic to ferromagnetic at (T-C) 80 K and a metal insulator transition at (T-MI) 77.5 K and at 2 mT magnetic field. The upturn of the resistance observed at low temperatures (<36 K) was attributed to the Coulomb blockade, and the strong structural disorder is due to the large lattice mismatch and strain relaxation. A large magnetoresistance ratio [MR %] of 780% was observed at 100 K and 6 T magnetic field.
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    LaBaMnO films produced by dip-coating on a quartz substrate
    (Elsevier Science Sa, 2008) Gencer, H.; Gunes, M.; Goktas, A.; Babur, Y.; Mutlu, H. I.; Atalay, S.
    The electrical transport and magnetoresistance properties of the polycrystalline La0.67Ba0.33MnO3 film produced on a quartz substrate were investigated first time. X-ray powder diffraction indicated that film sample has perovskite structure. Scanning electron microscope indicated that La0.67Ba0.33MnO3 film thickness is approximately 20 mu m and the average grain size of this sample varies between 8 and 10 mu m. La0.67Ba0.33MnO3 film showed a phase transition from paramagnetic to ferromagnetic at (Tc) 130 K and a metal-insulator transition at (T-MI) 137 K at 2 mT magnetic field. The upturn of the resistance observed at low temperatures (<49 K) was attributed to the Coulomb blockade and the strong structural disorder due to the large lattice mismatch and strain relaxation. A large magnetoresistance ratio (MR(%)) of 230% was observed at 125 K and 6 T magnetic fields. (C) 2007 Elsevier B.V. All rights reserved.
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    SIZE-INDUCED EFFECTS IN NANOSTRUCTURED NiFe2O4
    (World Scientific Publ Co Pte Ltd, 2010) Gunes, M.; Gencer, H.; Izgi, T.; Kolat, V. S.; Atalay, S.
    NiFe2O4 nanoparticles were successfully prepared by a hydrothermal process and the effect of temperature on them was studied. The particles were annealed at various temperatures ranging from 413 to 1473 K. Studies were carried out using powder X-ray diffraction, scanning electron microscopy, infrared spectroscopy, differential thermal analysis, thermogravimetric analysis and a vibrating sample magnetometer. The annealing temperature had a significant effect on the magnetic and structural parameters, such as the crystallite size, lattice parameter, magnetization and coercivity.