# Magnetic oxide of iron is

$(a)\;Fe_2O_3 \\(b)\;FeO\\(c)\; Fe_3O_4 \\ (d)\;Fe_4O_6$

It is ferrous ferric oxide of iron and exhibits permanent magnetism.
Iron(II,III) oxide is the chemical compound with formula $Fe_3O_4$. It occurs in nature as the mineral magnetite. It is one of a number of iron oxides, the others being iron(II) oxide (FeO), which is rare, and iron(III) oxide $(Fe_2O_3)$ also known as hematite. It contains both $Fe^{2+}$ and $Fe^{3+}$ ions and is sometimes formulated as FeO ∙ $Fe_2O_3$. This iron oxide is encountered in the laboratory as a black powder. It exhibits permanent magnetism and is ferrimagnetic.
Hence c is the correct answer.
edited Mar 27