Colossal Magnetoresistance in Screen Printed Manganite Films

Abstract

Thick films of La_0.67Ca_0.33MnO₃ 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 T_p1. T_p1 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 T_p1 (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 T_p1 (187 K) in an 8T applied field. The MR sensitivity as a function of field at T≪T_p1 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 T_p1 varies for these films from 253 to 26 K. The film sintered in air shows 65% MR around T_p1 (252 K) in an 8T applied field.

Thick films of La_0.63Y_0.07Ca_0.30MnO₃ 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 T_p1 ∼220 K. For both substrates, the films sintered in oxygen flow have slightly higher T_p1. 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 T_p1 (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≪T_p1.