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    Frequency dependence of the intergranular AC loss peak in a high-T-c Bi-(Pb)-Sr-Ca-Cu-O bulk superconductor
    (ELSEVIER SCIENCE BV, 1998) Celebi, S; Karaca, I; Aksu, E; Gencer, A
    We have performed AC susceptibility measurements as a function of temperature; frequency and AC field amplitude on a rectangular bar shaped high-temperature superconductor with nominal composition of Bi1.8.4Pb0.34Sr1.91Ca2.03Cu3.06O10 prepared by the liquid ammonium nitrate method. We have observed that as the frequency (AC field amplitude) increases, the intra- and intergranular AC loss peaks move higher (lower) temperature, which indicates that AC losses are due to both hysteretic bulk pinning losses and viscous (flux flow) losses. M-H curves exhibit a hysteresis which is similar to that of hysteretic superconductors. Activation energy at the grain boundary is extracted from the loss peak at some selected AC fields. Experimental results are qualitatively discussed in the framework of the critical state model (CSM). (C) 1998 Elsevier Science B.V. All rights reserved.
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    Magnetic behavior in Ce1-xTbxMn2Si2 silicides by XRD, DSC and AC susceptibility measurements
    (WILEY-V C H VERLAG GMBH, 2005) Kervan, S; Kilic, A; Aksu, E; Gencer, A
    The structural and magnetic properties the polycrystalline Ce1-xTbxMn2Si2 (0 <= x <= 1) compounds were studied by means of X-ray powder diffraction, AC susceptibility and differential scanning calorimetry (DSC). All compounds investigated crystallize in the body-centred tetragonal ThCr2Si2-type structure with the space group 14/mmm. Substitution of Tb for Ce leads to a linear decrease of the lattice constants and the unit cell volume. The lattice constants and the unit cell volume obey Vegard's law. At low temperatures, the rare earth sublattice orders and reconfigures the ordering in the Mn sublattice for x >= 0.2. The Neel temperature T-N(Mn) determined by DSC technique increases linearly with increasing Tb content x. The results are collected in the x-T magnetic phase diagram. (c) 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.