Spatial and temperature-evolved tunneling spectroscopic studies of La$_{0.7}$Ca$_{0.3}$MnO$_{3}$(LCMO) films and LCMO/organic-semiconductor heterostructures with spin-polarized scanning tunneling microscopy (SP-STM)

We report studies of spatially resolved tunneling spectra (TS) of La$_{0.7}$Ca$_{0.3}$MnO$_{3}$ (LCMO) (T$_{c}$ = 260K) epitaxial films and related heterostructures of tris(8-hydroxyquinoline) aluminum (Alq3)/(LCMO) using a UHV, variable temperature STM. At 77K with a Pt/Ir tip we observe sharp spatial transitions between two cluster types with disparate normalized conductance. The majority type region exhibits high conductance peaks at high bias (+/- 2V) and a low energy gap, consistent with band structure calculations. The minority type region reveals moderate conductance over the entire bias range, from -3V to +3V. In contrast, spin-polarized tunneling spectra taken with Cr-coated STM tips show a spatially varying low bias gap in all regions. Further experiments using SP-STM on LCMO under varying temperatures and applied magnetic fields and on Alq3/LCMO structures to study the spin transport length in Alq3 will be reported.