We propose to perform high resolution neutron diffraction on powder samples of the frustrated antiferromagnets Ag1-xCuxFe1-yGayO2 using HRPD. CuFe1-yGayO2 and AgFeO2 have different types of non-collinear magnetic orderings : proper screw helical and cycloid structure, respectively. Recent work suggested that the ferroelectricity induced by proper helical structure can be explained by the coupling between a macroscopic structural rotation (which is allowed in ferroaxial classes) and the magnetically induced structural chirality. Thus, the main purpose of this experiment is to identify the detailed structural distortion associated with the different types of magnetic orderings of Ag1-xCuxFe1-yGayO2 using HRPD.