Magnetic properties of lanthanum gallate doped with chromium, strontium, and magnesium demonstrating electronic-ionic conductivity were studied taking various ratios between the contents of Cr and diamagnetic elements. In the context of the diluted solution model invoking Heizenberg-Dirac-van Vleck theory the fractions of clusters and single chromium atoms were calculated for the series of LaCrxGa1-xO3-delta, La1-0.2xSr0.2xCrxGa1-xO3-delta, La1-0.5xSr0.5xCrxGa1-xO3-delta, LaCrxGa1-1.2xMg0.2xO3-delta, LaCrxGa1-1.5xMg0.5xO3-delta and La1-0.2xSr0.2xCrxGa1-1.2xMg0.2xO3-delta solid solutions (0.01 < x < 0.10). A substantial influence of the nature and concentration of heterovalent diamagnetic substituent was shown on the quantitative and qualitative composition of chromium atoms clusters incorporating strontium, magnesium, and oxygen vacancies, the clustering directly depending on the Cr:A ratio (A-Sr, Mg). (C) 2012 Elsevier B.V. All rights reserved.