La(0.7)Sr(0.3)MnO(3) thin films deposited by pulsed laser ablation for spintronic applications

Among spintronic materials, mixed-valence manganite La(0.7)Sr(0.3)MnO(3) (LSMO) is widely investigated due to its half-metal nature. LSMO thin films were grown by pulsed laser deposition (PLD) onto amorphous silica substrates heated at nearly 600 degrees C. An ArF excimer laser was chosen to induce ablation due to its more energetic photons compared to the other quoted excimer laser sources. Different oxygen pressures were considered in order to study the influence of oxygen on the LSMO optical and electrical properties. In this respect, the visible transparency percentage of the deposited films is found good enough for spin-OLED applications. The absorption coefficient shows an absorption band tunable as a function of the oxygen content. Its energetic location and evolution with the oxygen content demonstrate it originates from radiative transitions between the spin-majority bands separated by the Jahn-Teller distortion. All of this lets relate the deposition oxygen pressure to the Mn(3+) ion content in each film and interpret electrical data. The 200 and 100 nm thick samples exhibit weak metallic transport behavior at room temperature with a resistivity of 4.8 and 6.9 Omega cm, respectively. Concerning the resistivity response versus temperature, the measured low metal-insulator transition temperature (150 K) is related to the sample structural features as involved by the depositions. Two different transport mechanisms describe the conductivity regime of the deposited samples, namely the small polaron variable range hopping (VRH) and the Arrhenius law