  We use inelastic neutron scattering to study temperature and energy
dependence of spin excitations in optimally P-doped BaFe2(As0.7P0.3)2
superconductor (Tc = 30 K) throughout the Brillouin zone. In the undoped state,
spin waves and paramagnetic spin excitations of BaFe2As2 stem from
antiferromagnetic (AF) ordering wave vector QAF= (1/-1,0) and peaks near zone
boundary at (1/-1,1/-1) around 180 meV. Replacing 30% As by smaller P to induce
superconductivity, low-energy spin excitations of BaFe2(As0.7P0.3)2form a
resonance in the superconducting state and high-energy spin excitations now
peaks around 220 meV near (1/-1,1/-1). These results are consistent with
calculations from a combined density functional theory and dynamical mean field
theory, and suggest that the decreased average pnictogen height in
BaFe2(As0.7P0.3)2 reduces the strength of electron correlations and increases
the effective bandwidth of magnetic excitations.
