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

Abstract

A first principles study of La2−2xSr1+2xMn2O7 compounds for doping levels 0.3 ≤ x ≤ 0.5 shows that the low energy electronic structure of the majority spin carriers is determined by strong momentum dependent interactions between the Mn eg d x 2 −y 2 and d 3z 2 −r 2 orbitals, which in addition to an x dependent Jahn-Teller distortion, differ in the ferromagnetic and antiferromagnetic phases. The Fermi surface exhibits nesting behavior that is reflected by peaks in the static susceptibility, whose positions as a function of momentum have a non-trivial dependence on x.