  The electrical and magnetic response to a bias current has been investigated
in a singlecrystalline ferromagnetic manganese oxide
$\Pr_{0.8}$Ca$_{0.2}$MnO$_3$ . A significant decrease of the magnetization is
observed at the same threshold current where a non-linearity of V-I
characteristics appears. Such a behavior cannot be understood in the framework
of the filamentary picture usually invoked for the non linearity of the other
manganese oxides. Instead, an analogy with spintronic features might be useful
and experimental signatures seem to be in agreement with excitations of spin
waves by an electric current. This provides an example of a bulk system in
which the spin polarized current induces a macroscopic change in the
magnetization.
