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, La2−2xSr1+2xMn2O7, 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.

Orbital mixing and nesting in the bilayer manganites La$_{2-2x}$Sr$_{1+2x}$Mn$_2$O$_7$

“…But clearly, AF coupling acts to quench the bilayer splitting, with dramatic effects, particularly for the d 3z 2 −r 2 states. This is in line with very recent photoemission data that indicate a collapse of bilayer splitting near x=0.4 [21,22].…”