Multistep Accelerated Aging of Magnetic Field Sensors Based on Nanostructured La–Sr–Mn–O Thin Films
We present results of investigation of accelerated aging influence on electrical resistivity and magnetoresistance (MR) of nanostructured La–Sr–Mn–O films used for magnetic field sensors, which could be applied in advanced scientific and industrial devices. The 400-nm-thick manganite films were grown by metal organic chemical vapor deposition technique. To investigate the effectiveness of accelerated aging, the three methods were tested: 1) thermal treatment of the sensor samples at 100 °C temperature in Ar atmosphere when film surface was uncoated; 2) thermal treatment of the samples coated prior to treatment by polymer; and 3) multistep aging including both previous methods: thermal treatment of the samples with uncoated surface in Ar atmosphere and additional thermal treatment of the coated samples. The sensor samples were studied without and in pulsed magnetic field up to 20 T. To describe the underlying processes, the kinetics of resistivity change during accelerated aging was analyzed using a stretched exponent relaxation function. It was found that the best long-term stability of resistivity in time demonstrated samples treated by a multistep accelerated aging method. All three aging methods resulted in minor influence (<1%) on MR of the films in magnetic fields up to 20 T.
Magnetoresistant La1−xSrxMnO3 films by pulsed injection metal organic chemical vapor deposition: effect of deposition conditions, substrate material and film thickness
Abstract High quality epitaxial La 1− x Sr x MnO 3 films were deposited by pulsed injection metal organic chemical vapor deposition, using as precursor materials metal-2,2,6,6-tetramethyl-3,5-heptandionates dissolved in monoglyme. The influence of various deposition conditions, substrate material and film thickness on film properties was investigated. The best films were deposited on LaAlO 3 substrates at 825 °C: films exhibited a sharp semiconductor–metal transition and high magnetoresistance (∼40%) at a close-to-room temperature and in a rather low field of 1.5 T. In-situ or ex-situ high-temperature annealing in oxygen increased the temperature of semiconductor–metal transition, but decreased the magnetoresistance and the temperature coefficient of resistance. Biaxial strain imposed by the lattices’ mismatch was clearly observed in thinner La 1− x Sr x MnO 3 films on perovskite substrates. Tensile strain was present in the films on SrTiO 3 and compressive strain in the films on LaAlO 3 (and less clearly on NdGaO 3 ). Both tensile and compressive strains decreased the temperature of electric transition and the values of magnetoresistance. The strain was completely relaxed in the films more than ∼100 nm thick.
The lights that failed: European international history, 1919-1933
PART I: THE RECONSTRUCTION OF EUROPE, 1918-1929 1. The Hall of Mirrors: Peacemaking in the West 2. Distant Frontiers: Peacemaking in the East 3. Revolution from the Left: The Soviet Union and the Post-War Settlement 4. The Primacy of Economics: Reconstruction in Western Europe, 1919-1924 5. The Primacy of Nationalism: Reconstruction in Eastern and Central Europe 6. Revolution from the Right: Italy, 1919-25 7. The Geneva Dream: The League of Nations and Post-War Internationalism 8. New Dawn? Stabilisation in Western Europe after Locarno 9. Faltering Reconstruction: Cracks in the Locarno Facade 10. Troubled Waters: Uncertainties in Italy, Eastern Europe and the Soviet Union 11. Faltering Internationalism: Disarmament and Security after Locarno Conclusion: Europe Reconstructed? PART II: THE HINGE YEARS, 1930-1933 12. The Diplomacy of the Depression: Economics and Foreign Policy 13. Beyond Europe: The Manchurian Crisis 14. The Poisoned Chalice: The Pursuit of Disarmament Conclusion: The Hinge Years Appendices Select Bibliography