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Öğe An alternative measurement method for magneto-impedance effect in amorphous alloys(Elsevier Science Sa, 2001) Atalay, F; Atalay, SAn alternative measurement method for giant magneto-impedance (GMI) effect is described. The method measures pulse width instead of induced voltage between the ends of wire as a function of external applied field. In the measurement method two ac signals are applied to the wire and it has been shown that by changing the amplitude of the low-frequency ac signal a large variation in the field dependence of pulse width can be obtained. (C) 2001 Elsevier Science B.V. All rights reserved.Öğe Comparative study of magnetoimpedance effect in current and field annealed (Co0.9Fe0.05Ni0.05)75Si15B10 amorphous ribbons(Elsevier Science Bv, 2005) Atalay, SMagneto impedance (MI) and hysteresis loops in amorphous (Co0.9Fe0.05Ni0.05)(75)Si15B10 ribbons were measured to investigate the influence of current and field annealing. The results indicated that a transverse anisotropy was induced by both the magnetic field and current annealing methods. Using both techniques we succeeded in inducing the same magnitude of uniaxial anisotropy, K-u. It was observed that current annealed samples showed a larger MI effect. Since both samples have the same K-u, the difference in the magnitude of MI was explained by the domain structure. A positive MI effect, as large as 62%, was found in the 60 min current annealed sample at a 1 MHz driving frequency. (c) 2005 Elsevier B.V. All rights reserved.Öğe ?E effect in amorphous glass covered wires(Ieee-Inst Electrical Electronics Engineers Inc, 2000) Squire, PT; Atalay, S; Chiriac, HAmorphous Fe-Si-B glass-covered and glass-removed wires have been studied in the as-received state and after furnace annealing at 480 degrees C for various times. The M-H loops and magnetic field dependence of Young's modulus measurements have shown that the as-received, glass-covered wire has a single domain configuration with the easy axis parallel to the wire axis. It is suggested that the core-shell domain model applies in annealed, glass-covered and as-received wires after removal of the glass.Öğe The effect of annealing and crystallization on the magnetoelastic properties of Co-Si-B amorphous wires(Amer Inst Physics, 1996) Atkinson, D; Squire, PT; Atalay, SThe field dependence of Young's modulus (Delta E effect) of amorphous wires of Co72.5Si12.5B15 has been studied in the as-quenched state, and after annealing for times between one and several hundred minutes at temperatures of 450, 480, and 500 degrees C. In the as-quenched state the Delta E effect is small (<2%), because the quenching stresses couple with the magnetostriction (lambda(s) similar to-3X10(-6)) to produce significant anisotropy. Annealing for short times (>1 min) is sufficient to relieve much of the quenching stress, resulting in magnetic softening and enhanced Delta E effect (at best >30%). Further annealing eventually reverses these trends, increasing coercivity and anisotropy, and reducing the Delta E effect. This behavior is attributed to surface crystallization. The results are interpreted in terms of the core-shell domain model, and are consistent with the retention of a significant component of circumferential domain structure in the shell in all annealing conditions studied. (C) 1996 American Institute of Physics.Öğe Effect of different heat treatments on magnetoelastic properties of Fe-based amorphous wire(Elsevier Science Sa, 2001) Atalay, S; Adiguzel, HI; Kamer, OThe field dependence of Young's modulus of Fe77.5Si7.5B15 amorphous ferromagnetic wires were studied in as-quenched state and after furnace, current and pulse annealing. In as-quenched state, the change in Young's modulus as a function of field is small due to induced large anisotropy during the quenching process. Annealing for short times is sufficient to remove most of the quenched stresses resulting in magnetic softening and large change in Young's modulus. Further furnace or current annealing leads to surface crystallization which develops an easy axis in the circumferential direction, but such an easy axis was not observed in pulse annealed samples. The temperature of current annealed samples were calculated from resistance-temperature curve and the temperature of pulse annealed samples were estimated from T-t curve, where T is the annealing temperature and t the annealing time to reach the minimum value of coercivity. (C) 2001 Elsevier Science B.V. All rights reserved.Öğe The effect of furnace annealing and surface crystallization on the anisotropy, ?E and magnetoimpedance effects in Fe71Cr7Si9B13 amorphous wires(Iop Publishing Ltd, 2004) Bayri, N; Kolat, VS; Atalay, FE; Atalay, SThe dependence of the magnetization loops, coercivity, anisotropy constant, DeltaE and magnetoimpedance (MI) effects in positively magnetostrictive Fe71Cr7Si9B13 amorphous wires on annealing conditions were studied. Samples were annealed at temperatures of 440degreesC and 460degreesC for durations between 0.3 and 300 min. The results indicate that progressive annealing first leads to relief of internal stresses and annealing of wires at 460degreesC for 60 min produces the minimum coercivity of about 1 A m(-1). Further annealing increases the coercivity and anisotropy, due to partial crystallization at the surface. It was found that the anisotropy changes its direction to the circumferential direction with the surface crystallization. The maximum change in Young's modulus was measured to be about 75% in a partly surface crystalline sample. It was observed that the magnitude of the MI effect of the stress relieved sample could exceed 200% at 1 MHz.Öğe Effect of hydrogen charging on the electrochemical and magnetic properties of Fe73.5M1Nb3Si13.5B9 (M = Cu, Pt, Pd, Ag, Mn) alloys(Wiley-V C H Verlag Gmbh, 2002) Kolat, VS; Turkdemir, H; Adigüzel, HI; Atalay, FE; Atalay, S; Sovak, PThe effects of hydrogen absorption on the electrochemical, magnetic and magnetoelastic properties of amorphous Fe73.5M1Nb3Si13.5B9 alloys (M = Cu, Pt, Ag, Pd, Mn) were investigated. Hydrogen was charged cathodically for 30 min with cathodic current density of 50 A/m(2) in all samples using 0.5 M H2SO4 solution with 0.1 g/l As2O3 as a poison. It was observed that the partial substitution of Pt. Mn, Ag, Pd for Cu in Fe73.5Cu1Nb3Si13.5B9 has a great influence in the hydrogen absorption properties.Öğe Effect of pH on the magnetoimpedance properties of electrodeposited CoNiFe microtubes(Elsevier Science Bv, 2006) Atalay, FE; Kaya, H; Atalay, SCobalt/nickel/iron (CoNiFe) magnetic samples were prepared by electrodeposition onto copper wires with a diameter of 50 pin. The magnetic properties of CoNiFe microtubes were systematically investigated at pH 2-3.5. It was observed that the composition, surface quality and magnetic and magnetoimpedance (MI) properties of the CoNiFe magnetic tubes were strongly affected by the pH of the electrochemical bath. The MI ratio of 123.2% at 160 kHz and a coercivity of 51.5 A/m were obtained for the sample that was produced in the pH 2.4 solution. The energy dispersive X-ray spectrum was also evaluated; this film had a composition of 22.14% Co. 59.94% Ni and 17.92% Fe, with no impurities. (c) 2005 Published by Elsevier B.V.Öğe Effects of annealing on the magnetoelastic properties of Fe66Cr8Cu1Nb3Si13B9 ribbons(Ieee-Inst Electrical Electronics Engineers Inc, 1996) Squire, PT; Atalay, S; SlawskaWaniewska, AThe field dependence of Young's modulus has been measured in samples of Fe66Cr8Cu1Nb3Si13B9 alloy annealed to induce varying nanocrystalline fractions. The results are interpreted partly in terms of internal stress relief and reduced magnetostriction in the nanocrystalline samples. It is necessary to invoke magnetocrystalline anisotropy within the nanocrystalline grains to explain the behaviour after annealing at higher temperatures and for longer times.Öğe Giant magnetoimpedance effect in NiFe/Cu plated wire with various plating thicknesses(Elsevier Science Sa, 2005) Atalay, FE; Atalay, SIn this study, the magnetoimpedance, MI, effect in NiFe/Cu wire with various plated NiFe thicknesses was investigated. The MI results showed that the frequency, where the maximum MI occurs, decreases with increasing plating thickness. During the plating process some parameters such as the plating voltage, pH, and the temperature of solutions were kept constant. It was found that the thickness of the plated NiFe layer changes with plating time and the obtained plated layers are approximately 1-2, 3.5 and 10 mu m for 10, 60 and 180 min plating times, respectively. It was found that the NiFe film thickness had a significant effect on the magnitude and frequency dependence of the MI effect. The magnitude of the MI ratio under the H = 7400 A/m can reach about 750% for 180 min plating at 55 kHz driving current frequency. (c) 2004 Elsevier B.V. All rights reserved.Öğe Giant stress-impedance effect in Fe71Cr7Si9B13 amorphous wires(Elsevier Science Sa, 2004) Bayri, N; Atalay, SThe giant stress-impedance (SI) effect in as-received and furnace annealed Fe71Cr7Si9B13 amorphous wires is studied. Samples were annealed at temperature of 460degreesC for times between 0.3 and 300 min to remove internal stresses. The results show that the magnetoimpedance and SI effect change sharply with annealing and a maximum stress-impedance ratio of 255% is observed in the wire annealed for 10 min under an applied tensile stress of 250 MPa. (C) 2004 Elsevier B.V. All rights reserved.Öğe Hydrogen effect on the field dependence of Young's modulus of FeCuNbSiB alloy(Elsevier Science Sa, 2002) Kolat, VS; Bayri, N; Atalay, SThe magnitude of the magnetic field dependence of Young's modulus of FeCuNbSiB alloys was found to decrease after hydrogenation but to nearly recover after 2-3 h. A large variation in the magnetic and the magnetoelastic properties of as-received sample was observed after hydrogenation. DeltaE and M-H results of samples annealed at 450degreesC showed that annealing could reduce hydrogen permeation into the sample. Practically no variation in the magnetic and magnetoelastic properties of samples annealed at 550degreesC were observed before and after hydrogenation. (C) 2002 Elsevier Science B.V. All rights reserved.Öğe The influence of chromium content on the properties of Fe74-xCrxCu1Nb3Si13B9 alloys(Wiley-V C H Verlag Gmbh, 2002) Bayri, N; Adigüzel, HI; Atalay, S; Sovak, PIn this study, we have investigated the effect of Cr substitution on the structural, magnetic and magnetoelastic properties of Fe74-xCrxCu1Nb3Si13B9 (x = 2, 4, 8, 11, 14) alloys. The samples were annealed between 450 and 600 degreesC for 1 It under argon atmosphere to induce various nanocrystalline fractions. The change in microstructure upon annealing were examined by the X-ray spectrum data. A large influence of Cr content on the formation of alpha-FeSi phase was observed. The magnetic field dependence of the Young's modulus (DeltaE effect) was measured using the vibration reed method. The DeltaE results are interpreted partly in terms of the stress relief and the reduced magnetostriction in nanocrystalline samples.Öğe Influence of hydrogen charging on magnetic and magnetoimpedance properties of FeSiB and CoFeSiB amorphous wires(Elsevier Science Sa, 2005) Atalay, F; Atalay, SThe magnetic and magnetoimpedance (MI) effect properties of amorphous ferromagnetic Fe77.5Si7.5B15 and (Co0.94Fe0.06)(72.5)Si12.5B15 were studied before and after hydrogen charging by an electrochemical method. The hydrogen charging was carried out at 25 degrees C and in a stirred solution by applying a constant current density of 20 mA/cm(2) for 1 h. It was found that the saturation magnetization of FeSiB wire decreased from 1.6 to 1.345 T and the magnitude of the MI effect decreased from 24.4 to 7.1 after hydrogen charging. No remarkable variation in the shape of the magnetization loop and the MI effect in CoFeSiB wire were observed after hydrogenation. (c) 2005 Elsevier B.V. All rights reserved.Öğe Infrared absorption study of Fe2O3-CaO-SiO2 glass ceramics(Elsevier Science Sa, 2001) Atalay, S; Adiguzel, HI; Atalay, FThe ceramic lasses were prepared from extra pure reagents of Fe2O3, CaO and SiO2 powders. The 15 g batch was melted at 1550 degreesC, for 2 h in a platinum crucible. The glass structure was obtained by pouring the melt into a copper plate and pressing quickly by another copper plate. The glass structure was checked by XRD. IR studies were first made in ceramic glasses for various Fe contents. The 19.5Fe(2)O(3). 40.25CaO . 40.25SiO(2) glass sample was annealed at 750 degreesC under hydrogen atmosphere, hi the annealed sample new vibration bands were observed which were absent in the untreated samples, It was observed that the new peaks are mainly due re, the formation of beta -CaSiO3 (wollastonite) phases. (C) 2001 Elsevier Science B.V. All rights reserved.Öğe Low field magnetoimpedance in FeSiB and CoSiB amorphous wires(Elsevier Science Bv, 2004) Atalay, S; Bayri, NThe low magnetic field, H, dependence of real part of impedance, R, of as-received FeSiB and CoSiB wires have been investigated. The measurements were performed at various frequencies for various wire lengths. The wires with length longer than 7cm show sharp peaks in the R-H curves. The combination of R-H data with M-H data indicates the existence of interaction between motion of the domain wall in the inner core and the magnetic moments in the outer shell. (C) 2003 Elsevier B.V. All rights reserved.Öğe Magnetic and electrical properties of La0.67Ca0.33Mn0.9V0.1O3 two-phase composite(Elsevier, 2006) Kolat, VS; Gencer, H; Atalay, SIn this work, we present magnetic and electrical properties of La0.67Ca0.33Mn1-xVxO3 (x=0 and 0.1). Polycrystalline La0.67Ca0.33MnO3 and La0.67Ca0.33Mn0.9V0.1O3 samples were prepared by conventional solid-state reaction. Two Curie temperatures for the La0.67Ca0.33Mn0.9V0.1O3 sample were observed at T-c1 = 223 K and T-c2 = 190 K. The undoped La0.67Ca0.33MnO3 sample showed only one magnetic transition temperature at 267K. The temperature dependence of resistance showed two maxima in the V-doped sample, and the peak value of magnetoresistance (MR) around the Curie temperature increased with V doping. Double maxima ill the resistance-temperature and magnetisation-temperature Curves are explained by the existence of two phases ill La0.67Ca0.33Mn0.9V0.1O3 samples. (c) 2005 Elsevier B.V. All rights reserved.Öğe Magnetic and magnetoelastic properties of Fe-Si-B metallic fibers(Ieee-Inst Electrical Electronics Engineers Inc, 1996) Atalay, S; Squire, PT; Rudkowski, PAmorphous metallic Fe78Si9B13 fibers, 50 mu m in diameter, produced by the melt extraction method, have been studied in the as-quenched state and after furnace annealing at 455 degrees C and 480 degrees C for times between 0.5 min and 50 min. Measurements of the M-H loops and field dependence of Young's modulus have shown that they behave in a way very like that of amorphous wires. The minimum coercivity of 3 A/m is greater than that found in wires, and the minimum Young's modulus (similar to 0.45 times the saturation value) is greater. It is suggested that the core-shell domain model applies in the its-quenched state and that stress relief followed by surface crystallization dominate the anisotropy.Öğe Magnetic entropy change in Fe74-xCrxCu1Nb3Si13B9 (x=14 and 17) amorphous alloys(Elsevier Science Bv, 2005) Atalay, S; Gencer, H; Kolat, VSIn this study, the magnetic entropy variation in Fe74-xCrxCu1Nb3Si13B9 (x = 14 and 17) amorphous alloys was investigated. The temperature dependence of the magnetic entropy variation was calculated from the magnetization data. It was found that the Curie temperature of the sample decreases with increasing Cr content. The maximum entropy change corresponding to a magnetic field variation of 3 T is about 0.9 J/kg K for Fe60Cr14Cu1Nb3Si13B9 and 0.6 J/kg K for Fe57Cr17CU1Nb3Si13B9. (c) 2005 Elsevier B.V. All rights reserved.Öğe Magnetocaloric behaviour in Fe57Cr17Cu1Nb3Si13B9 soft magnetic alloys(Wiley-V C H Verlag Gmbh, 2004) Kolat, VS; Atalay, SIn this study, the magnetocaloric effect in as-received and nanocrystalline Fe57Cr17Cu1Nb3Si13B9 alloys in ribbon form was investigated The temperature dependence of the magnetic entropy variation, DeltaS(m), was calculated from the magnetisation data. It was found that the Curie temperature of the as-received amorphous sample is 156 K and the maximum entropy change occurs at this temperature. The calculated value of the maximum entropy change under 6 T magnetic field is about 1 J/kg.K in as-received amorphous ribbon and 1.12 J/kg.K for nanocrystalline sample under 5 T magnetic field.
