title: Spectacular doping dependence of interlayer exchange and other results on spin waves in bilayer manganites.
abstract: We report the measurement of spin waves in the bilayer colossal magnetoresistive manganites La2-2xSr1+2xMn2O7 with x = 0.30, 0.35, and 0.40. For x = 0.35 and 0.40 the entire acoustic and optic dispersion relations are well described by those for a bilayer Heisenberg Hamiltonian with nearest-neighbor exchange only, which is explained together with the spin-wave lifetimes by the double exchange model. The in-plane exchange depends weakly on x, but that between the planes of a bilayer changes by a factor of 4, directly revealing a change from mixed d(3z(2)-r(2)) and d(x(2)-y(2)) orbital character to mostly d(x(2)-y(2)).
authors.affiliation: ISIS Facility, CLRC Rutherford Appleton Laboratory, Didcot, Oxon OX11 0QX, United Kingdom.
authors.forename: T G
authors.initials: TG
authors.lastname: Perring
authors.forename: D T
authors.initials: DT
authors.lastname: Adroja
authors.forename: G
authors.initials: G
authors.lastname: Chaboussant
authors.forename: G
authors.initials: G
authors.lastname: Aeppli
authors.forename: T
authors.initials: T
authors.lastname: Kimura
authors.forename: Y
authors.initials: Y
authors.lastname: Tokura