Room Temperature Magnetoresistance at Low Magnetic Fields in La0.7 Ba0.3 MnO3.

This paper examines the possibility of enhancing the room temperature magnetoresistance at low applied magnetic fields in single layer La_0.7 Ba_0.3 MnO₃ thin films. The influence of lattice mismatch strain, as well as the effect of different frequency regimes, on the magnetoresistance is explored. The effects of lattice mismatch strain are studied by measuring the magnetoresistance as a function of the La_0.7 Ba_0.3 MnO₃ film thickness, oxygen annealing, and lattice matched buffer layers. We find that the release of the lattice mismatch strain improves the magnetoresistance at room temperature and at low magnetic fields. In fact, the highest magnetoresistance at room temperature (−1.7% at 500 Oe) has been found for the 1600 Å as-grown La_0.7 Ba_0.3 MnO₃ film, whereas the largest magnetoresistance (−1.9% at 500 Oe) is found at 309 K for the 1000 Å La_0.7 Ba_0.3 MnO₃ film annealed in flowing O₂ for 1 h at 900°C. Finally, we find that the microwave magnetoresistance is the same as the dc magnetoresistance when the cavity corrections are applied. In the single layer La_0.7 Ba_0.3 MnO₃ system, the low field magnetoresistance at room temperature is far from being technologically viable. [ABSTRACT FROM AUTHOR]