Microstructural and magnetic characterization were undertaken on high-rate, high-temperature grown YBa2Cu3O7–δ (YBCO) films. The films were of approximately 1 μm thickness and were grown by pulsed laser deposition on (100) SrTiO3 using a high-power industrial laser at growth temperatures between 750 °C and 870 °C and at growth rates of up to 4 μm/min. Two YBCO layers with different c-lattice parameters were observed in the films, the higher c value occurring near the substrate interface and arising from cation disorder and oxygen nonstoichiometry, and the lower one near the film surface arising from cation disorder alone. BaCuO2 precipitates were present near the surface of the films, indicative of partial melting during growth. The amount of BaCuO2 increased with growth temperature. Epitaxial Y2O3 also formed in increasing amounts suggestive of a different partial melting reaction in the films compared to bulk YBCO, where Y2BaCuO5 coexists with liquid. Around 1 MA/cm2 values of high critical current density (Jc) were observed in the films, and the in-field Jc improved with growth temperature despite the fact that the superconducting transition width increased significantly.

In order to achieve scalability in processing of IBAD conductors for commercial applications, rapid YBCO film growth rates are required. In this work, scanning Raman spectroscopy, X-ray diffraction, scanning electron microscopy and, microwave surface resistance have been used to study high rate grown YBCO films. The films were grown by pulsed laser deposition on (100) SrTiO3 using a high power industrial laser at growth temperatures from 750 to 870 °C and growth rates up to 4 μm/min.

We report a Raman study of the n=2 and n=3 Bi2-xPbxSr2Can-1CunO4+2n+delta high-temperature super conducting cuprates. We find that the frequency of the O(2)(Sr) A(1g) mode systematically decreases with additional oxygen in the weakly coupled BiO layers. We speculate that this could be due to an expansion of the Cu-O-Bi bond length caused by an oxygen-induced compression of the weakly coupled BiO layers. It is shown that approximately one half of the decrease in the frequency of the O(2)(Sr) A(1g) mode in Bi2Sr2Ca1-zYzCu2O8+delta reported by Kahihana et al. can be attributed to the effect of additional oxygen and hence charge transfer effects are negligible for this Raman mode. The effect of Pb on the frequency of the O(2)(Sr) A(18) mode, while being systematic, can not be explained. We attribute the small increase in hole concentration with increasing Pb concentration to a partial charge compensation by a reduction in oxygen content. We provide evidence that the 655 cm(-1) peak can be attributed to epical oxygen sites at the boundaries of the supercell induced by the incommensurate modulation in the BiO layers.

We have studied the effect of oxygen pressure (PO/sub 2/) during pulsed laser deposition on the properties of YBCO films, with particular attention power microwave surface resistance R/sub s/. Above a threshold oxygen pressure the properties of the films are nearly independent of PO/sub 2/ during deposition and are typical of high quality YBCO films. The films made below this threshold pressure have increased disorder which produces a reduced T/sub c/ and an expanded c-axis lattice parameter. However, these films also have significantly reduced low temperature R/sub s/, which is likely a direct result of the increased scattering in these films. Preliminary Raman measurements show no increase in the Y-Ba cation disorder in these low PO/sub 2/ films, so that different disorder mechanism must be present.

We present results of a systematic study of the effect of film deposition temperature on both the linear and nonlinear response of superconducting YBa/sub 2/Cu/sub 3/O/sub 7-/spl delta// (YBCO) thin films and devices at microwave frequencies. Measurements of the unpatterned films show that samples grown by pulsed laser deposition at a lower substrate temperature (740/spl deg/C) display a smaller low-temperature residual surface resistance compared to films grown at a higher substrate temperature (780/spl deg/C). However, the same films which display low residual surface resistance also show increased nonlinear effects (measured by third harmonic generation) at all temperatures. Analysis of these results suggests that the increased defects present in the films grown at the lower deposition temperature are responsible for both the lower surface resistance and the higher third harmonic generation observed in these samples. We discuss the consequences of these results for the simultaneous optimization of both linear and nonlinear microwave properties of HTS thin films and devices.

In this study the influence of annealing at reduced oxygen pressure on electrical transport, Raman active phonon modes and structural properties of several La0.7Ca0.3MnO3 thin films has been determined. The out-of-plane lattice parameters and some of the Raman phonon modes were found to be insensitive to oxygenation condition. The temperature at which the peak magnetoresistance occurs and other of the Raman phonon modes, are found to change continuously as a function of decreasing oxygen partial pressure. The Raman studies indicate that small variations of oxygen content induce a structural change.

Thin films of colossal magnetoresistance (MR) material La0.7Ca0.3MnO3 were implanted with 200 keV Cr ions over a range of fluence from 1×1013 to 5×1015 ions/cm2. Resistance measurements were made in zero and applied magnetic fields of up to 8 T. At fluences of 1×1014 and 5×1014 Cr+/cm2, the resistance was much greater than in the unimplanted material and the metal–insulator transition temperature was suppressed to values below 20 K. For the highest fluence (5×1015 ions/cm2), a reentrant metal–insulator-type transition was observed and the resistance dropped significantly. Furthermore, improvement in the low-field MR was observed between the virgin and high fluence implanted films for fields less than 500 mT. These results are interpreted in terms of changes in magnetic properties with depth, defect creation, and the influence of oxygen deficiency.

Thin films of colossal magnetoresistance material La 0.7 Ca 0.3 MnO 3 were implanted with different fluence 200keV Cr ions. Resistivity measurements in zero and applied fields of up to 8T were made in order to determine the effects of the implanted magnetic ions on the magnetoresistance (MR). As the Cr fluence was increased, the resistivity increased and the metal-insulator transition (MI) temperature was suppressed to values below the experimentally accessible temperature range as a result of oxygen loss and the creation of defects. However, for the highest fluence of 5x10 15 ions/cm 2 , a re-entrant metal-insulator type transition was observed. Furthermore a significant improvement in the low field MR was observed for fields less than 500mT. These results are interpreted in terms of substitution of Cr ions onto Mn sites and the creation of a magnetically inhomogeneous material and the influence of oxygen deficiency.

We report a Raman study of the n52 and n5 3B i 22xPbxSr2Can21CunO412n1d high-temperature super- conducting cuprates. We find that the frequency of the O~2!Sr A1g mode systematically decreases with addi- tional oxygen in the weakly coupled BiO layers. We speculate that this could be due to an expansion of the Cu-O-Bi bond length caused by an oxygen-induced compression of the weakly coupled BiO layers. It is shown that approximately one half of the decrease in the frequency of the O~2!Sr A1g mode in Bi2Sr2Ca12zYzCu2O81d reported by Kahihana et al. can be attributed to the effect of additional oxygen and hence charge transfer effects are negligible for this Raman mode. The effect of Pb on the frequency of the O~2!Sr A1g mode, while being systematic, can not be explained. We attribute the small increase in hole concentration with increasing Pb concentration to a partial charge compensation by a reduction in oxygen content. We provide evidence that the 655 cm 21 peak can be attributed to apical oxygen sites at the boundaries of the supercell induced by the incommensurate modulation in the BiO layers.