Room temperature magnetoresistance at low magnetic fields in La0.7Ba0.3MnO3

This paper examines the possibility of enhancing the room temperature magnetoresistance at low applied magnetic fields in single layer La0.7Ba0.3MnO3 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 La0.7Ba0.3MnO3 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 angstroms as-grown La0.7Ba0.3MnO3 film, whereas the largest magnetoresistance (-1.9% at 500 Oe) is found at 309 K for the 1000 angstroms La0.7B0.3MnO3 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 La0.7Ba0.3MnO3 system, the low field magnetoresistance at room temperature is far from being technologically viable.