The Development of Alkoxy-Based Sol -Gel Processing for Magnetoresistive Manganite Thin Films

Abstract

The cubic lattice parameters of the films (i.e., a = ∼ 3.90 A) were in excellent agreement with values published in the literature for bulk, polycrystalline powders. Typical grain sizes started at 10--15 nm, increasing to 20--25 nm by 750°C. For films deposited on Si(100), magnetoresistance was observed in specimens heat treated at 700°C and 750°C, and for platinized-Si(100), 650°C, 700°C, and 750°C. Magnetoresistive response improved with heat-treatment temperature for the more refractory La0.67Ba0.33MnO3 composition. The lead-doped counterpart offered the best property evolution, with TC = 320 K and TIM = 254 K by 750°C on platinized-Si(100). All corresponding transport curves were symmetric, demonstrating clear metal-insulator transitions (i.e., TIM). High resistivities (i.e., ∼ 106 O-cm) were attributed to the fine-grain microstructure. Weak-field cycling between +/-500 Oe yielded symmetrical loops with appreciable linear regions, a highly-desirable characteristic for magnetic sensing applications.