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This article presents a comparative study of persistent photo-induced magnetization in intermediate and low bandwidth perovskite manganite thin films, and analyzes the possible mechanisms for the observed differences in light of their structural and magnetic properties. Intermediate bandwidth manganite LaCaMnO (LCMO) and low bandwidth manganite PrCaMnO (PCMO), both show persistent change in magnetization under light. However, under illumination, while LCMO shows increased ferromagnetic (FM) interaction both in low and saturation field regime, PCMO shows increased FM interaction at low fields and decreased FM behavior near saturation fields. Also relaxation of photo-induced magnetization shows stretched exponential nature in LCMO compared to much faster relaxation, beyond detection limit in PCMO. Comparison between these two systems will provide important insight of the underlying physics of persistent photo-induced magnetization of perovskites manganites and will consequently facilitate their application in magneto-optical devices, photodiodes and photovoltaics. [ABSTRACT FROM AUTHOR]

The accommodation field, B*, is generally defined to be the field at which the cross over from single vortex pinning to collective pinning occurs. It is determined from magnetization curves as the point where the Jc plateau ends and it used as a convenient way of comparing the pinning properties of superconducting films. Similarly, the characteristic field, Bc, can be obtained from magneto-optical (MO) images from when the flux fronts meet in the middle of the film. The matching field, Bc at which there is one vortex line per pinning site, is sometimes thought to be the same as B*, but in BaZrO3-doped YBa2Cu3O7 films the calculated BΦ, is much higher than the observed B*. BΦ, can be determined from angular dependent transport measurements. All of the field values correspond to some special case in the flux pinning in the film and relate to Jc. In this work we have determined Bc, B * and BΦ, for different kinds of YBCO films using MO, magnetization and transport measurements to reveal the deeper meaning of the special fields. [ABSTRACT FROM AUTHOR]

We report the effect of 4 wt% BZO-doping in GdBCO thin films on (100) STO substrates with novel nanograined target materials deposited by pulsed laser deposition (PLD) method. X-ray diffraction, atomic force microscopy and magnetization measurements, which were made in particularly wide temperature and magnetic field range, were used to determine the structural and superconducting properties. The results were compared with ones of YBCO. The deposition temperature, Ts, is not very critical for GdBCO and it is found to be much lower in undoped and BZO-doped GdBCO than in YBCO. The BZO-doping of GdBCO enhanced the field dependence of critical current density, jc, at low temperatures. Furthermore, BZO-doping enhances the accommodation field, B*, below 60 K being clearly higher at 10 K in doped GdBCO than in YBCO. The pinning mechanism in GdBCO was concluded to be similar to that of YBCO. Our results clearly show that undoped and BZO-doped nanophase GdBCO is a very promising target material for applications as well as for coated conductors. [ABSTRACT FROM AUTHOR]

We have prepared YBCO nanopowder by the sol-gel route. The original powder contains weak links as observed by magnetization and microwave absorption measurements. Most of the weak links could be reduced by keeping the powder in ethanol for 30 min in an ultrasonic bath. It was also found that the ultrasonic bath does not affect the superconducting properties of the nanoparticles themselves. The modulation field applied in the microwave absorption measurements was found to have a large effect on the temperature dependence of the absorption. This phenomenon was explained with a phase diagram for the weak links. [ABSTRACT FROM AUTHOR]