Pseudo-gap to band gap transition in La$_{0.7}$Sr$_{0.3}$MnO$_{3}$ (LSMO) observed by optical reflectivity/absorption

Thin film La$_{0.7}$Sr$_{0.3}$MnO$_{3}$ (LSMO) is a prime candidate for highly spin-polarized magnetic-tunnel-junction memories. Due to its magnetic properties, it is also a good candidate for applications utilizing electrical control of magnetism when grown adjacent to a ferroelectric layer such as Pb(Ti/Zr)O$_{3}$ (PZT). Recently, Wu and others have seen the emergence of a band gap (~1eV) in LSMO thin films, when grown adjacent to PZT. Currently, it is understood that LSMO is a half-metal, with a pseudo-gap due to a low desity of states (DOS) near the Fermi level. The transition from pseudo-gap to band gap is not yet fully understood. It is therefore our aim to investigate the emergence of this band gap through optical reflectivity/absorption and thickness dependence experiments.