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In the paper we report experimental results of AC magnetization losses in a multi-filamentary BSCCO-2223 superconducting composite tape due to coaxial AC and DC magnetic fields subjected perpendicularly to the plane of the tape. Such superposition of magnetic fields usually leads to some reduction of magnetization losses. A distinguished minimum in the AC loss is observed, at a certain DC bias magnetic field and at a certain fixed magnetic field amplitude. It is shown that the minimum of the AC losses very strongly depends on magnetic history of the investigated tape, which is directly related to the magnetic flux trapping within tape's superconducting filaments region. Measurements were carried out with a sinusoidally varying magnetic fields at amplitudes up to 100 mT and a superimposed DC magnetic field up to 50 mT, at frequency range of 21-113 Hz. [ABSTRACT FROM AUTHOR]

Abstract: The DC magnetization and AC magnetic susceptibilities were measured for MgB2 single crystals, unsubstituted and carbon substituted with the composition of Mg(B0.94C0.06)2. AC magnetic losses were derived from the AC susceptibility data as a function of the AC amplitude and the DC bias magnetic field. From the DC magnetization loops critical current densities were derived as a function of temperature and DC field. Results show that the substitution with carbon decreases critical current densities at low external magnetic fields, in contrast to the well known effect of an increase of the critical current densities at higher magnetic fields. [Copyright &y& Elsevier]

The DC magnetization and AC complex magnetic susceptibilities were measured for MgB single crystals, unsubstituted and carbon substituted with the composition of Mg(BC). The measurements were performed in AC and DC magnetic fields oriented parallel to the c-axis of the crystals. From the DC magnetization loops and the AC susceptibility measurements, critical current densities ( J were derived as a function of temperature and the DC and AC magnetic fields. Results show that the substitution with carbon decreases J) at low magnetic fields, opposite to the well known effect of an increase of J at higher fields. AC magnetic losses were derived from the AC susceptibility data as a function of amplitude and the DC bias magnetic field. The AC losses were determined for temperatures of 0.6 and 0.7 of the transition temperature T, so close to the boiling points of LH and LNe, potential cooling media for magnesium diboride based composites. The results are analyzed and discussed in the context of the critical state model. [ABSTRACT FROM AUTHOR]

Stress dependencies of AC transport current losses, magnetization losses and total losses were investigated applying tensile stresses to an YBCO (IBAD/PLD) conductor. Measured transport current losses showed slight stress dependence in the range of 0∼1 GPa. That can be explained by stress dependence of the critical current of the conductor. The magnetization and total losses are less sensitive to the stress than the transport current losses. [ABSTRACT FROM AUTHOR]

In the work we present experimental results of AC magnetization losses reduction due to striation process in YBCO-123/Hastelloy coated conductors. The measurements were carried out in a sinusoidally varying external magnetic field, with amplitudes up to 100 mT, in a frequency range of 8.5-85.4 Hz, and at temperature of 77 K. The field was oriented perpendicularly to the face of the tapes. Sample tapes were successively patterned into a form of narrow, parallel strips, by means of a photoresist lithography and chemical wet etching technique. Experimental results are discussed in a framework of existing theoretical models for energy dissipation in thin films in perpendicular AC magnetic fields. [ABSTRACT FROM AUTHOR]

The paper reports an experimental study on AC loss characteristics of a YBCO coated tape conductor carrying AC transport current in AC external magnetic field. In the experiment we electrically measured total losses that were transport current losses plus magnetization losses in AC external magnetic fields perpendicular to the tape surfaces. The transport current losses were measured by a four terminal method and the magnetization losses by a method using a pick-up coil. To measure the total losses electrically we need to pay proper attentions to prevent electromagnetic coupling between the sample currents and the external magnetic fields and to suppress inductive voltage in signals from the pick-up coil and voltage taps. The total losses were purely hysteretic for the amplitude of the external field up to 20 mT and the peak transport current up to the critical current. The loss characteristics can be explained by a theory based on the Bean model if the dependence of the critical current on the external magnetic field is taken into consideration. [ABSTRACT FROM AUTHOR]