Two kinds of magnetic fluids with different volume fractions are symmetrically filled into the W0.9 photonic
crystal waveguide structure. The 2D plane-wave expansion method is used to investigate the slow light
properties numerically. The constant group index criterion is employed to evaluate the slow light performance. The wavelength bandwidth Δλ centering at λ₀ = 1550 nm varies from 32.4 to 44.2 nm when the magnetic field factor α_|| changes from 0 to 1. And the corresponding normalized delay bandwidth product can be tuned from 0.221 to 0.258. For comparison and optimization, two infiltration cases are investigated and the more advantageous infiltration scheme is found.