Er 3 Fe 5-x Al x O 12 (0.0 ≤ x ≤ 0.8) garnets were prepared at 1300 ºC by ball milling method. Rietveld refinement of the samples revealed a garnet structure with Ia3d symmetry. The lattice parameter, cell volume, X-ray density and magnetization of the prepared garnets decreased with the increase of Al content (x). The coercivity of the garnets increased with x, but remained generally low, being below 20 Oe. Low temperature magnetic measurements versus temperature indicated that the magnetization of x = 0.0 exhibited a compensation temperature at ˗186º C, however, x = 0.8 exhibited a minimum at a higher temperature of ˗134º C.