Oxygen doping in Sr3Fe2O7-x is of special interest because it allows us to continuously tunethe magnetic interactions and dimensionality in a strongly correlated system. strongly correlatedsystem. The observed change in the ordered magnetic structure, from the helicalincommensurate (for x=0.0) to the commensurate (with k = (0, 0, 1) for x = 0.5), with oxygen doping confirms a change in the nature of the exchange interactions. In addition, the crystal structure for Sr3Fe2O6.5 changes from orthogonal to tetragonal upon heating to 335 K and the compound does?t order magnetically, if it is quenched to 2 K (from 335 K), which we believe is due to the fact that system is now 2D Heisenberg AFM (the bridging oxygen connecting the two Fe layers is disordered). We plan to measure the magnetic excitation in this magnetically disordered sate using the MERLIN TOF spectrometer.