We present 450 \mu m polarimetric observations of the M17 molecular cloud obtained with the SHARP polarimeter at the Caltech Submillimeter Observatory . Across the observed region , the magnetic field orientation is consistent with previous submillimeter and far-infrared polarization measurements . Our observations are centered on a region of the molecular cloud that has been compressed by stellar winds from a cluster of OB stars . We have compared these new data with previous 350 \mu m polarimetry and find an anti-correlation between the 450 to 350 \mu m polarization magnitude ratio and the ratio of 21 cm to 450 \mu m intensity . The polarization ratio is lower near the east end of the studied region where the cloud is exposed to stellar winds and radiation . At the west end of the region , the polarization ratio is higher . We interpret the varying polarization spectrum as evidence supporting the radiative alignment torque ( RAT ) model for grain alignment , implying higher alignment efficiency in the region that is exposed to a higher anisotropic radiation field .