A first principles study of ${\mathrm{La}}_{2-2x}{\mathrm{Sr}}_{1+2x}{\mathrm{Mn}}_2{\mathrm{O}}_7$ compounds for doping levels $0.3\le x\le 0.5$ shows that the low energy electronic structure of the majority spin carriers is determined by strong momentum-dependent interactions between the Mn $e_g$ $d_{x^2-y^2}$ 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 nontrivial dependence on $x$.

• Received 19 July 2008

DOI:https://doi.org/10.1103/PhysRevLett.101.236402