New magnetic materials derived from chromium dioxide

A new oxidative method of preparation of the chromium dioxide from Cr
2
O
3
is described. For the improvement of magnetic properties, in particular coercive field, of such a ferromagnetic oxide a substitution by rhodium +IV leads to the new interesting material Cr
1-x
Rh
x
O
2
with needlike particles (
H_{c} \simeq 500
Oe).