The compositional influence of Cr and Y on the microstructure of Mg-Cr-O, and Mg-Y-O films synthesized by reactive magnetron sputtering has been investigated by transmission electron microscopy, X-ray diffraction and molecular dynamics simulations. A decrease in crystallinity is observed in these films as the M (Cr or Y) content is increased. It is found that M forms a solid solution with MgO for metal ratios up to similar to 70% and similar to 50% for Cr and Y respectively. Above similar to 70% Cr metal ratio the Mg-Cr-O films are found to be completely amorphous. The Mg-Y-O films are composed of Mg(Y)O and Y(2)O(3) nano crystallites. up to similar to 50% Y metal ratio. Above this ratio, only Y(2)O(3) nano crystallites are found. The preferential < 111 > MgO grain alignment is strongly affected by the increase in M content. For M metal ratios up to similar to 50%, there is a selective promotion of the < 100 > MgO grain alignments and a decline in the < 111 > grain alignments. (C) 2011 Elsevier B.V. All rights reserved.