Abstract
We fabricated ferromagnetic La0.8Ba0.2MnO3 thin films and systematically investigated the Curie temperature (Tc) for film thickness dependence. Tc was defined as a maximum peak of a dM/dT. We found that the Tc gradually increased with decreasing film thickness from Tc of the bulk (270 K). The 20-nm-thick film showed a maximum peak of Tc (= 310 K) against the thickness and a Tc decreased blow 20-nm-thick film. However, even the ultra thin film with 5 nm thickness had a Tc of 290 K, near room temperature. In order to apply this result to an application working at room temperature, we constructed field-effect transistor structures using the ferromagnetic (La,Ba)MnO3 ultra thin film with the aim of controlling the metal-insulator transition at room temperature by applying an electric field. Investigations revealed that the transition temperature changed from 237.0 K to 242.0 K for the La0.90Ba0.10MnO3 channel layer by ferroelectric remnant polarity (±50 μC/cm2) and from 280.5 K to 283.0 K (±26 μC/cm2) for the La0.85Ba0.15MnO3 channel layer. These shifts, which were linearly proportional to the magnitude of ferroelectric remnant polarization, are induced by the accumulative charge due to the electric field.
