Aydogan, H.C. | Yilmaz, A. | Dorosinskii, L. | Topal, U.
Article | 2011 | Journal of Superconductivity and Novel Magnetism24 ( 01.02.2020 ) , pp.727 - 729
In the present study, we investigate the influence of boron oxide addition on magnetic and structural properties of some ferric compounds (BaFe 12O19 and BiFeO3). Our studies have shown that small amounts of B2O3 addition improve the crystalline structure, and thus improve the magnetic properties effectively. For instance, remanence and saturation magnetization of hard magnetic BaFe12O 19 increases by half. Similar behavior was also observed in the BiFeO3 system. There are two possible explanations for these improvements: (1) Boron atoms reside between the grains and improve the links between grains or (2) Boron substitutes for iron . . . atoms and changes magnetic anisotropy and thus magnetic parameters. © Springer Science+Business Media, LLC 2010
Topal, U. | Coker, E.G. | Alıkma, F. | Kolemen, U. | Uzun, O.
Article | 2014 | Journal of Superconductivity and Novel Magnetism27 ( 1 ) , pp.133 - 141
The second harmonic signal, which is generated by co-application of AC and DC fields to polycrystalline type-II superconductors, were analyzed in terms of the weak links and the critical current density. With this aim the YBa 2 Cu 3-x Zn x O 7-y (x=0, 0.01, 0.02, 0.03, 0.05, and 0.1) samples were synthesized in order to adjust intergranular couplings and thus the strength of weak links. The mechanical and magnetic measurements are in good agreement on that Zn doping reduces strength of the links between grains; however, contrary to the common expectations, it has no direct contribution to the 2nd harmonic signal strength. © 2013 Spr . . .inger Science+Business Media New York
Topal, U. | Alıkma, F. | Gulce Coker, E.
Article | 2013 | Journal of Superconductivity and Novel Magnetism26 ( 5 ) , pp.1831 - 1835
In this study a novel type of magnetometer capable of direct measurement of DC fields as low as 0.5 nT was described. The second harmonic voltage generated by polycrystalline superconductors inserted in AC and DC fields was used as sensor signal. The experiments have shown that a 0.5 nT DC field can be detectable by using Bi-2223 superconductors as the core material. The Bi-2223 reveals better sensitivity compared to the other high-Tc cuprates. Besides, the sensor works in a wide dynamical range (105 orders in magnitude), which increases its potential application areas. © Springer Science+Business Media New York 2012.
Alikma, F. | Birlikseven, C. | Gulmez, G. | Turhan, E. | Coker, E.G. | Topal, U.
Article | 2012 | Journal of Superconductivity and Novel Magnetism25 ( 7 ) , pp.2539 - 2545
In this study we report on some critical factors affecting the sensitivity of a magnetic field sensor whose working principle is based on a linear DC field dependence of the second harmonic of the AC response in polycrystalline type-II superconductors. DC-fields down to 2 nT in magnitude could be detected by finding optimal conditions. The optimal sensor design was determined by studying superconductor cores having different geometries and coil configurations. The optimal AC-field frequency, which is required for excitation of the specimen, was found to be 50 kHz. The second harmonic signal changes quite linearly with the DC-field u . . .p to 0.1 Oe. © Springer Science+Business Media, LLC 2012
Gülce Çoker, E. | Kolemen, U. | Topal, U.
Article | 2014 | Journal of Superconductivity and Novel Magnetism28 ( 2 ) , pp.513 - 518
The effect of the intergranular couplings on the second harmonic of the fundamental signal, which is generated by co-application of DC and AC fields to a magnetic material having nonlinear magnetization, was investigated on B 2O3 doped YBaCuO superconductors. Physical and mechanical properties of B 2O3 doped YBaCuO superconductors were also analyzed to support electrical measurements. © 2014, Springer Science+Business Media New York.
Coker, E.G. | Yetgin, N. | Yildiz, E. | Alikma, F. | Acar, E. | Topal, U.
Conference Object | 2013 | Journal of Superconductivity and Novel Magnetism26 ( 4 ) , pp.1011 - 1014
In the present study, we have investigated the influence of different types of doping elements on magnetic properties of M-type BaFe12O 19 samples. It was observed that Nb2O5 addition increases the coercive field, the remanence magnetization (Mr), and saturation magnetization (Ms) values by about 27 %, 47 %, and 53 %, respectively. In the same manner, MnO2 also improves the magnetic parameters significantly. The Mr and Ms values show increments up to 40 % in magnitude. On the other hand, the best magnetic properties were achieved by the addition of CuO to the B2O 3 doped BaFe12O19. These materials have M r and Ms values up to ~34 em . . .u/g and ~62 emu/g, respectively. © 2012 Springer Science+Business Media New York