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Asymmetric ?E Effect and its Use as a Magnetic Field Sensor
(Polish Acad Sciences Inst Physics, 2019) Atalay, S.; Kolat, V. S.; Izgi, T.
The Delta E effect was studied using Fe77B16Si5Cr2 amorphous ribbon, and asymmetry in the Delta E curves was created using micro magnets placed on the surface of the ribbon. Asymmetry was also observed in the vibration amplitude versus the magnetic field, and magnetization loops of amorphous ribbons with micro magnets were observed. The results show that the asymmetries in the Delta E curves and magnetisation loops are in agreement with each other. A linear change in vibration amplitude as a function of the applied magnetic field in the +/- 100 A/m region was observed, which is important for sensor applications.
Asymmetric giant magnetoimpedance effect created by micro magnets
(Elsevier Science Bv, 2018) Atalay, S.; Izgi, T.; Buznikov, N. A.; Kolat, V. S.
Asymmetric giant magnetoimpedance (AGMI) effect has been investigated in as-prepared and current annealed amorphous (Co0.9Fe0.05Ni0.05)(75)Si15B10 ribbons. Asymmetry was created by micro magnets. Different numbers of magnets were used and it was found that increasing number of magnet, the shift in AGMI curves increases. When two micro magnets were placed 1 cm away from the ends of ribbon, a distortion in two peak shape of the GMI curve was observed. At high frequency range, a linear change in the AGMI was observed for the current annealed sample. (C) 2018 Elsevier B.V. All rights reserved.
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.
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.
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.
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.
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.
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.
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.
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.
Electrical Transport and Magnetoresistance of La0.67Ca0.33MnO3: Agx (x=0, 0.1, 0.2, 0.3, 0.4) Composites
(Korean Magnetics Soc, 2012) Gencer, H.; Pektas, M.; Babur, Y.; Kolat, V. S.; Izgi, T.; Atalay, S.
The structural, magnetic and magnetotransport properties of La0.67Ca0.33MnO3: Ag-x (x = 0, 0.1, 0.2, 0.3 and 0.4) composites were investigated systematically. X-ray and EDX analysis indicated that Ag is not substituted into the main La0.67Ca0.33MnO3 phase and remains an additive to the second phase at the grain boundary. The Curie temperature first decreased from 269 K for x = 0 to 257 K for x = 0.1 and then remained nearly unchanged with increasing Ag content. For the x > 0.1 samples, a second transition temperature (T-M12) was observed in the resistance curves. At temperatures below 150 K, a significant enhancement in MR was observed while high temperature MR decreased with increasing Ag content. The maximum MR was observed to be 55% in the x = 0.4 sample at 10 K and a 6T magnetic field, this value is larger than that of pure La0.67Ca0.33MnO3 (53% at 265 K and 6 T). In addition, at low fields (H < 1T), a sharp increase in the MR was observed.
Field Induced Unusual Magnetic Behavior at Low Temperature in Pr0.67Ca0.33MnO3
(Polish Acad Sciences Inst Physics, 2014) Pektas, M.; Gencer, H.; Izgi, T.; Kolat, V. S.; Atalay, S.
In this study, magnetic properties of Pr0.67Ca0.33MnO3 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.
Formation and Detection of Magnetic CoNiFe Nanowire Network Using Magnetoelastic Sensor
(Springer, 2019) Atalay, S.; Kaya, H.; Atalay, F. E.; Izgi, T.; Kolat, V. S.
In this study, CoNiFe magnetic nanowires were detected using a magnetoelastic sensor (ME) without any coating. Amorphous ferromagnetic ribbon of Metglass 2826 (Fe40Ni38Mo4B18) was used as a magnetoelastic sensor. The magnetoelastic ribbons were drop coated with Co12Ni64Fe24 magnetic nanowires in order to study how the mass deposition affects the resonance frequency and to determine the amount of coated nanowire. It was found that the minimum amount of detected nanowire can be as low as 200 ng. It was also shown that the nanowire network was developed on the surface of Metglass 2826 MB magnetoelastic sensor.
Influence of Ferromagnetic Ribbon Width on Q Factor and Magnetoelastic Resonance Frequency
(Polish Acad Sciences Inst Physics, 2021) Atalay, S.; Inan, O. O.; Kolat, V. S.; Izgi, T.
In this study, Fe40Ni38Mo4B18 (2826MB) amorphous ferromagnetic ribbons were used as a magnetoelastic sensor. The variation in resonance frequency and quality (Q) factor values of samples with a 30 mm length and different widths is investigated as a function of a magnetic field. It is observed that as the sample width increases, the change in resonance frequency and the Q factor both decrease. The parameter Q x amplitude/M is defined to understand the effect of a ribbon width on the resonance curve. According to this parameter, samples with 1 and 2 mm widths are found to have a better magnetoelastic effect.
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.
Influence of Si substitution on the structural, magnetic and magnetocaloric properties of Gd55Co20Fe5Al20-xSix alloys
(Elsevier, 2013) Atalay, S.; Gencer, H.; Kaya, A. O.; Kolat, V. S.; Izgi, T.
The structural, magnetic and magnetocaloric properties of Gd55Co20Fe5Al20-xSix (x=0, 2, 5, 10, 15, 20) alloys have been investigated in detail for the first time. The broad diffraction peaks for x=0 and 2 indicated that the samples have amorphous structures. For higher Si content (x >= 5), some diffraction peaks revealed that the Si substitution increases the crystallinity of the alloys. While the magnetization curves showed only one magnetic transition for low Si content, for the higher concentrations a second magnetic transition was observed due to the crystallization of the samples. The maximum entropy change of 8.01 J/kg K was observed in a 5 T magnetic field for the x=0 sample and decreased with further increase of Si concentration. The refrigerant capacities vary from 913 J/kg for x=0 to 596 J/kg for x=15. (C) 2013 Elsevier B.V. All rights reserved.
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.
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.
Magnetic and Magnetocaloric Properties of (Gd1-xCex)Al2 (x=0, 0.25, 0.5, 0.75) Compounds
(Korean Magnetics Soc, 2011) Gencer, H.; Izgi, T.; Kolat, V. S.; Kaya, A. O.; Atalay, S.
The magnetic and magnetocaloric properties of Gd1-xCexAl2 (x = 0, 0.25, 0.5, 0.75) intermetallic compounds alloys have been investigated in detail for the first time. XRD patterns indicated that all the samples were crystallized in a single phase with MgCu2-type structure (Laves phase). Ce substitution for Gd increased the lattice parameters and decreased the Curie temperature from 163 K for x = 0 to 37 K for x = 0.75. A maximum entropy change of 3.82 J/kg K was observed when a 2 T magnetic field was applied to the x = 0 sample. This entropy change decreased with increasing Ce content to 2.04,J/kg K for the x = 0.75 sample.
Magnetic and magnetocaloric properties of GdB2 compound
(Natl Inst Optoelectronics, 2012) Gencer, H.; Izgi, T.; Kolat, V. S.; Atalay, S.
In this study, magnetic and magnetocaloric properties of GdB2 compound were first time investigated.GdB2 compound was prepared by arc-melting method. The magnetic characterizations of the samples were defined at various temperatures and magnetic fields. Saturation magnetization value is 19.5 emu/g at 275 K. The magnetic entropy change of the GdB2 compound was calculated from the isothermal magnetization curves under the different magnetic fields. The peak value of vertical bar Delta S-m vertical bar is 1.89 J/kg K under the applied field changing from 0 T to 4 T. The adiabatic temperature change was calculated from heat capacity. The peak value of Delta T-ad is 0.49 K at 1 T magnetic field.

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