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Öğe Coil-less fluxgate effect in (Co0.94Fe0.06)72.5Si12.5B15 amorphous wires(Elsevier Science Bv, 2010) Atalay, S.; Ripka, P.; Bayri, N.In this study, the coil-less fluxgate properties of the as-cast and annealed amorphous wires with the composition (Co0.94Fe0.06)(72.5)Si12.5B15 were investigated. As its name implies, a coil-less fluxgate is a new type of magnetic-field sensor without a coil. When the wire is periodically saturated in a magnetic field in the circumferential direction with a 30 kHz, 62 mA driving current under a 16.5 pi rad/m torsional strain, there is a linear variation in the second harmonic of the voltage from the wire ends as a function of the applied external DC magnetic field along the length of the wire. Current-stress annealing of each sample improved the sensitivity of the coil-less fluxgate sensor. This is the first time that it has been shown that a linear change in the output of the coil-less fluxgate sensor. This is the first time that it has been shown that a linear change in the output of the coil-less fluxgate sensor can be obtained using torsion annealed wire without the necessity of twisting the wire during measurement. We showed that the linear operating range of the sensor can be increased by increasing the demagnetization factor in the sensing direction, so that the coil-less fluxgate sensor can be miniaturised just by reducing the wire length. (C) 2010 Elsevier B. V. All rights reserved.Öğe Coil-less Fluxgate Effect in Amorphous Co71Fe1Mo1Mn4Si14B9 Ribbon(Trans Tech Publications Ltd, 2012) Fidan, A.; Atalay, S.; Bayri, N.; Atalay, F. E.; Yagmur, V.In this study, the coil-less fluxgate effect in Co71Fe1Mo1Mn4Si14B9 amorphous ribbon was investigated. The coil-less fluxgate is a new type of fluxgate sensor without a coil. It is based on helical anisotropy and deep circumferential magnetic saturation in the ferromagnetic fluxgate core. Coil-less fluxgate measurements were performed in as-cast and annealed ribbons at 480 mA current with 3, 12.5 and 25 rad/m torsion. The second harmonic of the output voltage detected from the ends of the wire show a linear variation in the low magnetic field region. The sensitivity of the current annealed ribbons in the presence of 25 rad/m torsion is about 570 V/T, which is comparable with previously reported fluxgate sensitivity values. The presented sensor has no coil so it is much easier to reduce the size of the sensor and easy to fabricate it.Öğe Coil-less fluxgate effect in amorphous wires(Elsevier Science Sa, 2010) Atalay, S.; Bayri, N.; Izgi, T.; Atalay, F. E.; Kolat, V. S.In this study, the coil-less fluxgate properties of as-received amorphous microwires with the compositions (Co(0.94)Fe(0.06))(72.5)Si(12.5)B(15), Fe(77.5)Si(7.5)B(15) and Co(72.5)Si(12.5)B(15) have been investigated. As its name implies, a coil-less fluxgate is a new type of magnetic field sensor without a coil. When the (Co(0.94)Fe(0.06))(72.5)Si(12.5)B(15) wire is magnetically saturated in the circumferential direction with a 30 kHz and 48 mA driving current and under the effect of 33 pi rad/m torsional strain, there is a linear variation in the second harmonic of the voltage from wire ends, U(wire) as a function of the applied external dc magnetic field, H(z), along the wire length. The slope of the second harmonic versus H(z) curve changes in opposite directions as the direction of torsional strain changes from the positive to the negative direction. Coil-less fluxgate effects in as-received Fe(77.5)Si(7.5)B(15) and Co(72.5)Si(12.5)B(15) wires have also been investigated. A very small change in the second harmonic of voltage U(wire) is observed in Fe(77.5)Si(7.5)B(15) wire, with some small hysteresis. (C) 2010 Elsevier B.V. All rights reserved.Öğe Coil-less fluxgate effect in CoNiFe/Cu wire electrodeposited under torsion(Elsevier, 2011) Atalay, S.; Yagmur, V.; Atalay, F. E.; Bayri, N.Co19Ni49.6Fe31.4 layer was electrodeposited onto a twisted Cu wire and helical anisotropy was induced in the magnetic Co19Ni49.6Fe31.4 shell. The magnetic and coil-less fluxgate (CF) properties are presented. The Co19Ni49.6Fe31.4/Cu wire, produced at zero torsional strain, shows a CF output of nearly zero. The samples produced under torsional strains of 29.5 pi and 59 pi rad/m show a linear change in CF output in the low-frequency range. At higher frequencies the CF output shows two linear ranges. A maximum sensitivity of 150V/T is observed at 20 kHz driving-current frequency and 67 mA driving current for a wire produced under 59 pi rad/m torsional strain. It is also found that the slope of the CF curve depends on the direction of induced anisotropy. (C) 2011 Elsevier B.V. All rights reserved.Öğe Coil-Less Fluxgate Effect in Negatively Magnetostrictive Co72.5Si12.5B15 Amorphous Wire(Amer Scientific Publishers, 2013) Atalay, S.; Bayri, N.; Fidan, A.; Yagmur, V.; Izgi, T.; Atalay, F. E.; Kolat, V. S.In this study, we have investigated coil-less fluxgate (CF) properties of as-cast and annealed Co72.5Si12.5.B15 amorphous wire. As-cast wire without any torsional strain shows nearly zero output in the second harmonic. When the as-cast wire is twisted a linear variation in the second harmonic of output was obtained as a function of applied magnetic field. It was also shown that a linear change in the output of the coil-less fluxgate sensor can be obtained using torsion annealed wire without twisting the wire during measurement. The second harmonic of U-wire showed a linear dependence at magnetic fields of +/- 400 A/m and the sensitivity of the sensor at 50 kHz frequency is about 75 V/T at 61 mA ac driving-current frequency for the wire annealed at 525 mA dc current for 20 minutes at 500 MPa tensile stress and 33 pi rad/m torsional strain.Öğe Crack Detection Using Fluxgate Magnetic Field Sensor(Polish Acad Sciences Inst Physics, 2014) Izgi, T.; Goktepe, M.; Bayri, N.; Kolat, V. S.; Atalay, S.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)Fec(0.06))(72.5)Si2.5B15 amorphous ferromagnetic wire was placed inside a pickup coil winding with 50 mu m 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.Öğe Crystallisation Kinetics of Co75-xMxSi15B10 (M = Fe, Mn, Cr and x=0, 5) Amorphous Alloys(Polish Acad Sciences Inst Physics, 2016) Bayri, N.; Kolat, V. S.; Izgi, T.; Atalay, S.; Gencer, H.; Sovak, P.In this study, the effect of Fe, Mn and Cr substitution for Co on the crystallization kinetics of amorphous Co75-xMxSi15B10 (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.Öğe The crystallisation kinetics, magnetic and magnetocaloric properties of Gd55Co20Fe5Al20 - xSix (x=0, 5, 10, 15) alloys(Elsevier, 2013) Gencer, H.; Izgi, T.; Kolat, V. S.; Bayri, N.; Kaya, A. O.; Atalay, S.The effects of substituting Si for Al on the crystallisation kinetics and magnetic and magnetocaloric properties of Gd55Co20Fe5Al20 Si-- x(x) (x = 0, 5, 10, 15) alloys have been investigated in detail. The broad diffraction peaks in the XRD patterns indicated that all the samples have amorphous structures. The activation energies of the alloys were calculated using the 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 increase in the activation energy as the Si content increased to x = 10 indicated that the addition of Si improves the thermal stability and slows the crystallisation kinetics of the samples. The value of the Avrami exponent showed that the nucleation and growth mechanisms of the crystallisation process depend on the Si concentration. The maximum entropy change reached a maximum value of 6.82 J/kg K for x = 5 and then decreased with further increases of Si. The refrigeration capacities are 558, 665,700 and 519 J/kg for x = 0, 5, 10 and 15, respectively. The increased thermal stabilities and large refrigeration capacities make these amorphous alloys attractive candidates for magnetic refrigeration applications. (C) 2013 Elsevier B.V. All rights reserved.Öğe 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.Öğe The Dynamic Effects in Electrodeposited NiFe/Cu Wire with Preliminary Torsion(Trans Tech Publications Ltd, 2012) Yagmur, V.; Atalay, F. E.; Bayri, N.; Atalay, S.Ni80Fe20/Cu composite wires were produced under torsion using electrodeposition method. The total length of the magnetic film deposited onto 50 mu m Cu wire is 3 cm and the thickness of the magnetic layer is about 10 gm. All samples showed single peak in magnetoimpedance (MI) curves. The magnitude (Delta Z/Z) % are 260%, 235% and 119% for samples produced under 22.4, 44.8, 89.7 rad/m torsion values, respectively at driving frequency of 160 kHz. MI effect magnitude decreases with increasing applied torsion during the electrodeposition process. A linear change in the second harmonics of output voltage from wire ends as a function of applied magnetic field (coil-less fluxgate effect) was observed in all sample. The sensitivity of coil-less output increases with increasing torsion and maximum sensitivity was observed in the sample produced at 89.7 rad/m torsion.Öğe Effect of Fe Substitution on Magnetic and Magnetocaloric Properties of La0.94Bi0.06Mn1-xFexO3 (x=0, 0.05, 0.075 and 0.1) Compounds(Korean Magnetics Soc, 2017) Gencer, H.; Kolat, V. S.; Bayri, N.; Izgi, T.; Atalay, S.The effects of Fe doping on structural, magnetic and magnetocaloric properties of La0.94Bi0.06Mn1-xFexO3 (x = 0, 0.05, 0.075, 0.1) compounds were investigated. X-ray analyses showed that the substitution of Mn by Fe produced no major structural change. It was found that the saturation magnetization, Curie temperature and maximum value of magnetic entropy change decrease with increasing Fe content. The decrease in magnetic entropy change was attributed to the decrease in saturation magnetization and the nature of phase transition transforms from first-order to second-order. The refrigeration capacities were determined to be 259 and 230 J/kg for the x = 0 and 0.075 samples, respectively at a field change of 5 T.Öğe Effect of tensile stress on magnetoimpedance properties of CoNiFe/Cu wire(Iop Publishing Ltd, 2009) Bayri, N.; Kolat, V. S.; Kaya, H.; Atalay, F. E.; Izgi, T.; Atalay, S.A Co20.5Ni40.5Fe39 magnetic film was electrodeposited onto a copper wire 50 mu m in diameter. The magnetoimpedance (MI) effect, (Delta Z/Z)(H)(%) = ((Z(H)-Z(max))/Z(max)) x 100, was measured in the Co20.5Ni40.5Fe39/Cu composite wire under varying tensile stresses up to 30 MPa. The results showed that large MI and stress impedance (SI) effects can be observed in the Co20.5Ni40.5Fe39/Cu composite wire. The MI curve at zero tensile stress shows a small split peak in the low-field region. With increasing applied tensile stress, single-peak behaviour of the MI effect is observed. The magnitude of the MI and SI effects decreases with increasing tensile stress, sigma. The peak values of (Delta Z/Z)(H)(%) for the sample decrease from 265% at sigma = 0 to 39% at sigma = 30MPa at 40 kHz ac driving-current frequency. The impedance of a sample under the effect of 25 MPa tensile stress at 40 kHz ac driving-current frequency showed variations of about 146%. It was also found that the frequency value, f*, where the maximum MI effect was observed as a function of driving-current frequency, increases with increasing tensile stress.Öğe Effects of Ru substitution on the structural, magnetic and magnetocaloric properties of Pr0.68Ca0.22Sr0.1Mn1-xRuxO3(x=0, 0.05, 0.1 and 0.2) compounds(Springer, 2020) Pektas, M.; Izgi, T.; Gencer, H.; Atalay, S.; Kolat, V. S.; Bayri, N.The structural, magnetic and magnetocaloric properties of polycrystalline Pr0.68Ca0.22Sr0.1Mn1-xRuxO3(x = 0, 0.05, 0.1 and 0.2) compounds were studied. All the samples crystallized in an orthorhombic symmetry. A significant increase in the lattice parameters in the doped samples was attributed to the existence of Ru with a the mixed-valence state (Ru3+/Ru4+). The increase in the Curie temperature (T-c) with increasing Ru content was interpreted as Ru doping promoting the ferromagnetic interactions between Ru4+-Mn(3+)and Ru4+-Mn(4+)pairs. The decrease in saturation magnetisation was attributed to an AFM interaction between the Ru3+-Mn(3+)and Ru3+-Mn(4+)pairs and smaller magnetic moments of Ru than those of Mn. The decrease in |Delta S-M| (from 4.66 J kg(-1) K(-1)forx = 0.05 to 2.32 J kg(-1) K(-1)forx = 0.2 at 5 T) was attributed to the nature of phase transition (from a first-order to second-order transition) and a decrease in the saturation magnetisation.Öğe Influence of Ge and Bi substitution on the magnetic and magnetocaloric properties of LaFe11.4Si1.6(Natl Inst Optoelectronics, 2010) Kolat, V. S.; Kaya, A. O.; Izgi, T.; Gencer, H.; Bayri, N.; Atalay, S.In this work, the magnetic and magnetocaloric properties of LaFe11.4S1.6-xGex (x = 0.05, 0.1 and 0.2) and La1-xBixFe11.4Si1.6 (x = 0, 0.1 and 0.2) compounds have been investigated. X-ray results indicate that the samples with lower Ge and Bi contents mainly consist of the NaZn13-type phase with a small amount of alpha-Fe impurity phase. The alpha-Fe impurity phase increases with increasing concentrations of Ge and Bi. The Curie temperature of the samples also increases slightly with increasing Ge and Bi contents. The spin-wave dispersion coefficient D, exchange constant J and average mean-square range of exchange interaction ()(1/2) have been calculated. The increase in Curie temperature is attributed to an increase in the average Fe-Fe distance and ferromagnetic interactions. The peak values of the magnetic entropy change vertical bar Delta S-m vertical bar are found to decrease with increasing Ge and Si contents. This is attributed to a change of the phase transition from first order to second order. The peak values of vertical bar Delta S-m vertical bar are 22.38 J/kg K for LaFe11.4Si1.6, 12.58 J/kg K for LaFe11.4Si1.5Ge0.1 and 14.25 J/kg K for La0.9Bi0.1Fe11.4Si1.6 at a magnetic field of 6 T.Öğe Influence of the wire length on the of coil-less fluxgate properties of amorphous (Co0.94Fe0.06)72.5Si12.5B15 wire(Elsevier Science Sa, 2010) Atalay, S.; Bayri, N.; Izgi, T.; Yagmur, V.; Atalay, F. E.; Kolat, V. S.In this study, the coil-less fluxgate (CF) properties of amorphous (Co0.94Fe0.06)(72.5)Si12.5B15 wire, current-annealed at 450 mA dc for 15 min under 500 MPa tensile stress and 16.57 pi rad/m torsional strain, have been investigated. A CF is a new type of magnetic-field sensor without a coil. The dependence of the second harmonic of the output voltage from the wire ends, U-wire, on an external magnetic field in the longitudinal direction, H-z, for the frequency range 5-50 kHz and various values of the ac current I-wire is presented. The results show that the sensitivity of the CF depends on the frequency and I-wire. Even at a very low frequency (5 kHz). a pronounced variation in the behaviour of the CF sensor is observed. A 60-mm long sensor has a maximum sensitivity of 78.5V/T in a +/- 400 A/m linear operating range at 57 mA driving current. The sensitivity decreases but the linear operating range increases with decreasing wire length. A miniaturized 2.2-mm CF sensor shows similar to 0.4V/T sensitivity in a +/- 3000A/m linear operating range at 53 mA driving current and 50 kHz ac driving-current frequency. (C) 2010 Elsevier B.V. All rights reserved.Öğe 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.Öğe Magnetic and Magnetocaloric Properties of La0.94Bi0.06Mn1-xCrxO3 (x=0, 0.05, 0.1, 0.15, 0.2, 0.25) Samples(Polish Acad Sciences Inst Physics, 2019) Gencer, H.; Ozkan, U.; Bayri, N.; Izgi, T.; Kolat, V. S.The effects of Cr doping on structural, magnetic and magnetocaloric properties of La0.94Bi0.06Mn1-xCrxO3 (x = 0, 0.05, 0.1, 0.15, 0.2, 0.25) samples were investigated. It has been observed in X-ray analyses that the substitution of Mn by Cr produced no remarkable structural change and only the diffraction peaks for orthorhombic symmetry were obtained for all samples. The decrease in the Curie temperature and saturation magnetization with Cr content could be due to weakening of the ferromagnetism in Cr doped samples. The decrease in magnetic entropy change was attributed to the decrease in saturation magnetization with increasing Cr content.Öğe 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.Öğe Magnetic and Magnetoelastic Properties of Annealed Cold-Drawn CoSiB Amorphous Wires(Springer, 2015) Atalay, S.; Bayri, N.; Kolat, V. S.; Izgi, T.The dependence of the magnetisation loops, coercivity, anisotropy constant and Delta E effect (the change of Young's modulus as a function of the magnetic field) was studied in negatively magnetostrictive Co Si-72.5 (12.5) B (15) cold-drawn amorphous wires, with a mean diameter of 100 A mu m, under annealing conditions. Samples were annealed at a temperature of 460 C-a similar to for time periods between 0.3 and 1300 min. The results indicated that progressive annealing initially led to relief of the internal stresses and that annealing of the wire at 460 C-a similar to for 90 min produced the minimum coercivity, which was similar to 0.0063 Oe. Further annealing increased the coercivity and anisotropy due to partial crystallisation at the surface. The maximum change in Young's modulus was similar to 27 % and was seen in the wire that was annealed for 60 min.Öğe Magnetic and magnetoimpedance properties of Mn-doped FINEMET(Elsevier Science Bv, 2009) Kolat, V. S.; Bayri, N.; Michalik, S.; Izgi, T.; Sovak, P.; Atalay, F. E.; Gencer, H.In this study, the effect of substituting Mn for Fe on the magnetic and magnetoimpedance (MI) properties of amorphous and nanocrystalline Fe73.5-xMnxCu1Nb3Si13.5B9 (x = 1, 3, 5, 7) alloys has been investigated. A higher Mn content causes a decrease in the saturation magnetization and Curie temperature. For as-received Fe73.5-xMnxCu1Nb3Si13.5B9 (x = 0, 1, 3, 5, 7) ribbons, the measured values of the MI are 11%, 12%, 16%, 12% and 15% for x = 0, 1, 3, 5, 7, respectively. The magnitude of the MI ratio increases in annealed samples, indicating that they are magnetically softened by nanocrystallisation. The change in MI is found to be similar to 70% for the x = 3 sample annealed at 550 degrees C. It is also found that replacing a small amount of Fe by Mn improves the magnetic softness of Fe73.5-xMnxCu1Nb3Si13.5B9 alloys. (C) 2009 Elsevier B.V. All rights reserved.
