Bilayer splitting and c-axis coupling in bilayer manganites showing colossal magnetoresistance

Abstract

By performing angle-resolved photoemission spectroscopy of the bilayer colossal magnetoresistive (CMR) manganite, $L{a}_{2-2x}S{r}_{1+2x}M{n}_2{O}_7$, we provide the complete mapping of the Fermi level spectral weight topology. Clear and unambiguous bilayer splitting of the in-plane 3d${}_{x^2-y^2}$ band, mapped throughout the Brillouin zone, and the full mapping of the 3d${}_{3z^2-r^2}$ band are reported. Peculiar doping and temperature dependencies of these bands imply that as transition from the ferromagnetic metallic phase approaches, either as a function of doping or temperature, coherence along the c-axis between planes within the bilayer is lost, resulting in reduced interplane coupling. These results suggest that interplane coupling plays a large role in the CMR transition.

8 pages, 6 figures