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We have studied the electrical and magnetic properties of normal and superconducting states of RuGd1.6Ce0.4Sr2Cu2O10–δ (Ru-1222) system, prepared by the standard solid-state reaction technique, with applied magnetic field. The resistivity curves show that at high temperature the system is paramagnetic. At lower temperature, we can observe two magnetic transitions from paramagnetic state to anti-ferromagnetic and from anti-ferromagnetic to ferromagnetic. At room temperature the resistivity of sample shows insulating behavior and superconducting transition occurs at 45 K. Superconducting and magnetic parameters such as superconducting transition temperature Tc, magnetic transition Tirr, have been obtained through resistivity curve as a function of external magnetic field. We have observed that samples become superconductor at Tc which decrease from 49 K to 38 K with external magnetic field up to 1.6 T. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

The flux jumps, the second peak and the irreversible magnetic field in the magnetization hysteresis cycles have been investigated in the high temperature superconductor YBa2Cu3O7−δ single crystals. These cycles were obtained for different temperature values, the applied magnetic fields up to 6 T and the angle θ between the applied magnetic field and c-axis. The magnetization curves exhibit a remarkable second peak “fishtail”, this second peak was not observed for the low temperature, but we observed the flux jumps “saw tooth”. The temperature dependence of the irreversible magnetic field, Hirr, for the applied magnetic field perpendicular to the ab planes is given by an extended expression, Hirr α (1−T/Tc )α, where α is a constant, the Abrikosov flux dynamics can explain this behavior. The Hirr as a function of θ has been strongly influenced by the flux pinning and the thermally assisted flux motion. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Material– and flow properties of magnetic fluids can be influenced by applying an external magnetic field. In this work we will particularly consider the onset of convection in magnetic fluids which is influenced by a magnetic force. In a horizontal magnetic fluid layer the force arises if a temperature gradient and an external magnetic field is applied. The behaviour of the onset of convection is investigated for a static and a time–modulated magnetic field. For the case of a static magnetic field the onset of convection depends on the strength of the field and for a time–modulated magnetic field an additional dependence on the frequency of magnetic field variation is found. The experimental results presented here confirm in principle the theoretical predictions about the influence of static and time–modulated magnetic forces on the onset of convection. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Existing theories are not suited for explaining the stability of superconductors in a rapidly fluctuating magnetic field. Therefore, an attempt was made to study the stability of superconductors in such a magnetic field. Special attention is given to magnetic diffusion in the flux creep condition and dependence of the flux jumping on the fluctuation of magnetic field is explained. It has been proposed in the past that the maximum magnetic field first flux jump which a superconductor can shield without flux jumping is proportional to 1/3 to 1/2 power of the speed of magnetic field increase. The relation between the rate of field increase and the flux jump formation field was determined. Using a single strand Nb-48% Ti wire, the effect of copper ratio, the presence or absence of insulating varnish, copper foil, and the magnetic field sweep rate on the initiation of flux jumps was studied.

The ac loss in the nonuniform type-II superconducting wire in a longitudinal magnetic field decreases as the field increases. In the past, it has been explained that this decrease is due to a pinning effect by which the pinning force is increased with increasing field. However, the authors' results indicate that the pinning force actually decreases. 13 references.