  We perform a theoretical study of the magnetism induced in transition metal
dioxides ZrO2 and TiO2 by substitution of the cation by a vacancy or an
impurity from the groups 1A or 2A of the periodic table, where the impurity is
either K or Ca. In the present study both supercell and embedded cluster
methods are used. It is demonstrated that the vacancy and the K-impurity leads
to a robust induced magnetic moment on the surrounding O-atoms for both the
cubic ZrO2 and rutile TiO2 host crystals. On the other hand it is shown that
Ca-impurity leads to a non magnetic state. The native O-vacancy does not induce
a magnetic moment in the host dioxide crystal.
