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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 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.Öğe 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.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 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 field sensor using the asymmetric giant magnetoimpedance effect created by micromagnets(Springer, 2021) Pektas, M.; Kolat, V. S.; Bayri, N.; Izgi, T.; Atalay, S.A magnetic field sensor was developed using the asymmetric giant magnetoimpedance (AGMI) effect. Amorphous ferromagnetic (Fe0.06Co0.94)(72.5)Si12.5B15 wires were used in this study. The 2-cm-long wire showed an approximately 88% giant magnetoimpedance effect, and the 7-cm-long wire showed an approximately 197% giant magnetoimpedance effect. When two micromagnets were placed 1 cm from the ends of the wire, a distortion in the two peak shapes of the GMI curve was observed, and asymmetry was created by the micromagnets. The 7-cm-long wire showed an approximately 148% AGMI effect. A simple and a new approach was designed to develop a magnetic field sensor. In the design circuit, two signal generators were used to arrange the linearity and dc offset in the output signal. The circuit output showed good linearity and zero hysteresis in the +/- 250 A/m and +/- 50 A/m magnetic field regions for the 2-cm-long and 7-cm-long wires, respectively.Öğe Structural, Magnetic and Magnetocaloric Properties of Pr0.68Ca0.32-x Bi x MnO3 (x=0, 0.1, 0.18, 0.26 and 0.32) Compounds(Springer, 2016) Gencer, H.; Izgi, T.; Bayri, N.; Pektas, M.; Kolat, V. S.; Atalay, S.The structural, magnetic and magnetocaloric properties of the polycrystalline Pr0.68Ca0.32-x Bi (x) MnO3 (x = 0, 0.1, 0.18, 0.26 and 0.32) samples were studied. X-ray analyses indicated that all samples have a single phase of orthorhombic symmetry. The charge-order transition was observed for the x = 0 sample at T (CO)= 200 K, and it disappears with further Bi doping of the sample. The Curie temperature, saturation magnetisation and magnetocaloric effect decrease with increasing Bi content. The decrease in Curie temperature and saturation magnetisation was attributed to magnetic inhomogeneity and weakening of double-exchange interaction in the Bi-doped samples. The decrease in saturation magnetisation and the changed nature of phase transition give rise to a decrease in magnetic entropy change.Öğe Structural, magnetic and magnetocaloric properties of Ru doped Pr0.67Ca0.33Mn1-xRuxO3 manganites(Springer, 2022) Kanikirmizi, T.; Izgi, T.; Bayri, N.; Gencer, H.; Kolat, V. S.; Pektas, M.; Atalay, S.We have investigated the influence of ruthenium doping on magnetic and magnetocaloric properties of Pr0.67Ca0.33Mn1 - x RuxO3 (x = 0, 0.05, 0.1, 0.15, 0.2, 0.3, 0.5) compounds. X-ray results revealed that the samples have an orthorhombic structure with Pnma space group. The magnetization analysis also showed that Ru doping destroys CO antiferromagnetic and simultaneously inducing ferromagnetism. Variation of lattice parameters and magnetization measurements revealed the existence of mixed valence states of Ru3+ and Ru4+. With increasing Ru content, a slight increase in Curie temperature and magnetization values was observed until x = 0.15. At further Ru doping rates, a considerable decrease was observed in Curie temperature and saturation magnetization. Such a behavior at high Ru concentration rates in saturation magnetization and Curie temperature was attributed to a smaller magnetic moment of Ru4+ than that of Mn3+ and Mn4+ and increase of AFM interaction between the Ru3+- Mn3+ and Ru3+- Mn4+ pairs. The decrease in |Delta S-m| was attributed to the second-order magnetic phase transition and the reduction in saturation magnetization.Öğe Structural, magnetic, and magnetocaloric properties of (1-x)La0.7Ca0.3MnO3/(x)La0.7Ag0.3MnO3 composites(Springer, 2022) Yigiter, N.; Pektas, M.; Kolat, V. S.; Izgi, T.; Bayri, N.; Gencer, H.; Atalay, S.In this study, structural, magnetic, and magnetocaloric properties of (1 - x)La0.7Ca0.3MnO3/(x)La0.7Ag0.3MnO3 (x = 0, 0.25, 0.50, 0.75, and 1) composites were investigated in detail. The X-ray diffraction has indicated that the samples have a single phase without any detectable impurity. SEM analysis revealed that samples consist of irregularly shaped and strongly connected particles and grain boundaries become unclear with increasing x. The magnetic measurements revealed that the parent compounds exhibit a ferromagnetic to paramagnetic phase transition. The magnetization curves for composite samples exhibited two magnetic phase transitions nearly same temperature that of the parent compounds. The maximum value of magnetic entropy change (| increment S-m|) decreased from 8.02 for x = 0 to 4.1 J/kg K for x = 0.75 at 5 T magnetic field change. Overlapping entropy peaks becomes almost flat over a wide temperature range for composite samples inducing an enhancement of the RCP (= 273.96 J/kg for x = 0.75 at 5 T magnetic field change). Arrott plots showed a second-order magnetic phase transition for composite samples and also confirmed in terms of Landau theory.
