Magnetic iron oxide particles

An acicular magnetic iron oxide particle comprising a Co-modified acicular magnetic iron oxide core particle containing ferrous, a Zn compound layer of 0.1 to 5% by weight, calculated as Zn, based on the Co-modified acicular magnetic iron oxide core particle containing ferrous, as a lower coating layer on the surface of said core particle, and a layer of compounds containing Si and at least one metal selected from Al, Ca, Zr, Sb, Ti, V, Mg, Ba and Zn, of 0.05 to 5% by weight, calculated as SiO.sub.2 plus said metal element(s), based on the Co-modified acicular magnetic iron oxide core particle containing ferrous, as an upper coating layer thereon, wherein

• the weight ratio of the Zn compound layer to the compound layer containing Si and said metal(s) is 0.2-5/1 and the molar ratio of the Si compound to said metal(s) compound of the upper layer is 1-10/1, and the acicular iron oxide particle has a major axial diameter of 0.05 to 0.35 .mu.m, an axial ratio (major axial diameter/minor axial diameter) of not less than 5.0, a coercive force of 600 to 1200 Oe and exhibits a smaller percent reduction in Fe.sup.2+ content after seven days in air at 60.degree. C. and 90% RH than said acicular magnetic iron oxide particle in which either the Zn compound layer or the layer of compounds containing Si and said at least one metal is absent or where the Zn compound is the upper coating layer and the compounds containing Si and said at least one metal are the lower coating layer on the surface of said core particle.