The present invention concerns a stabilized ferromagnetic chromium dioxide and a process for obtaining the same. More particularly, the present invention relates to ferromagnetic chromium dioxide stabilized by means of the coating of its particles with a stabilizing substance, characterized in that the stabilizing substance is selected from the group consisting of a zinc, aluminum or chromium (III) polyphosphates having a high molar ratio phosphorus/metal and having, depending on the metal, the following formula: P.sub.2 O.sub.5.nZnO.mH.sub.2 O wherein "n" in general is comprised between 0.286 and 0.667 while "m" is generally comprised between 0 and 2.570;P.sub.2 o.sub.5.nAl.sub.2 O.sub.3.mH.sub.2 O wherein "n" is in general comprised between 0.225 and 0.500, while "m" is generally comprised between 0 and 2.68;P.sub.2 o.sub.5.nCr.sub.2 O.sub.3.mH.sub.2 O wherein "n" is in general comprised between 0.143 and 0.333, while "m" is generally comprised between 0.002 and 2.46.