Nanoparticles of  powders with composition MgAl₂O₄ and Pr_xMg_1-xAl₂O₄, where x = 0.05 and 0.10 were synthesized using low combustion method for precursors – the corresponding metal complexes of malonic acid dihydrazides. It is established that the metal complex precursor decomposes at 250–300⁰C with the combustion of the organic materials and the formation of alloyed substances of amorphous structure. X-ray studies have revealed that at 1200⁰C spinel crystal structure of MgAl₂O₄, Pr_0.05Mg_0.95Al₂O₄ and Pr_0.1Mg_0.9Al₂O₄ are fully formed, average size of nanoparticles making up 12.5, 12.9 and 14 nm respectively.