Thick films of La0.67Ca0.33MnO3 were fabricated on single crystal (100) LaAlO3 (LAO), single crystal (100) yttria stabilised zirconia (YSZ) and polycrystalline Al2O3 by a screen printing technique. The films were sintered at 1200, 1300 and 1400°C, in air, oxygen and nitrogen atmospheres to explore the optimum annealing conditions of manganite thick films. The thick films on LAO exhibit a M-I transition at Tp1. Tp1 varies from 180 to 258K depending on sintering temperature and atmospheres for these films. The thick film sintered at 1300°C in air shows highest (80%) MR at 8T near Tp1 (180 K). The thick films on YSZ also show a M-I transition in the measured temperature range except for the film sintered at 1400°C in nitrogen. The Tp1s for the thick films on YSZ varied from 187 to 265 K. The film sintered at 1400°C in oxygen exhibits 94% MR around Tp1 (187 K) in an 8T applied field. The MR sensitivity as a function of field at T≪Tp1 is highest for the oxygen sintered samples for the films on both LAO and YSZ substrates. The thick films fabricated on Al2O3 substrates reacted very badly for the films sintered at 1300 and 1400°C and are not suitable for further investigations. However, the films sintered at 1200°C in air, oxygen and nitrogen atmospheres show a M-I transition. The Tp1 varies for these films from 253 to 26 K. The film sintered in air shows 65% MR around Tp1 (252 K) in an 8T applied field.
Thick films of La0.63Y0.07Ca0.30MnO3 were fabricated on (100) LAO and polycrystalline Al2O3 substrates. The films were sintered at 1200°C in air and oxygen. All these thick films show a M-I transition at Tp1 ∼220 K. For both substrates, the films sintered in oxygen flow have slightly higher Tp1. The film on Al2O3 sintered in oxygen flow shows 71% MR at 220K in presence of an 8T applied field.
The salient feature of the CMR observed in these thick films are that MR is not limited to a small temperature window near Tp1 (e.g. epitaxial thin films, single crystal). The MR peak is very broad and for some films a temperature independent CMR is observed at T≪Tp1.
Bulk Sample Thick Film Yttria Stabilise Zirconia Apply Physic Letter Colossal Magnetoresistance
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A. K. M. Akther Hossain, L. F. Cohen, F. Damay, A. Berenov, J. MacManus Driscoll, N. McN. Alford, N. D. Mathur, M. G. Blamire, and J. E. Evetts., Journal of Magnetism and Magnetic Materials 192, 263 (1999)CrossRefADSGoogle Scholar