Room-temperature ferromagnetism in Sn1-xMnxO2 nanocrystalline thin films prepared by ultrasonic spray pyrolysis

Sn1-xMnxO2 (x = 0.01-0.05) thin films were synthesized on quartz substrate using an inexpensive ultrasonic spray pyrolysis technique. The influence of doping concentration and substrate temperature on structural and magnetic properties of Sn1-xMnxO2 thin films was systematically investigated. X-ray diffraction (XRD) studies of these films reflect that the Mn3+ ions have substituted Sn4+ ions without changing the tetragonal rutile structure of pure SnO2. A linear increase in c-axis lattice constant has been observed with corresponding increase in Mn concentration. No impurity phase was detected in XRD patterns even after doping 5 at% of Mn. A systematic change in magnetic behavior from ferromagnetic to paramagnetic was observed with increase in substrate temperature from 500 to 700 degrees C for Sn1-xMnxO2 (X = 0.01) films, Magnetic studies reveal room-temperature ferromagnetism (RTFM) with 3.61 x 10(-4) emu saturation magnetization and 92 Oe coercivity in case of Sn1-xMnxO2 (x = 0.01) films deposited at 500 degrees C. However, paramagnetic behavior was observed for the films deposited at a higher substrate temperature of 700 degrees C. The presence of room-temperature ferromagnetism in these films was observed to have an intrinsic origin and could be obtained by controlling the substrate temperature and Mn doping concentration. (C) 2009 Elsevier B.V. All rights reserved.