  We have studied the ferromagnetic Kondo lattice model (FKLM) with an Anderson
impurity on finite chains with numerical techniques. We are particularly
interested in the metallic ferromagnetic phase of the FKLM. This model could
describe either a quantum dot coupled to one-dimensional ferromagnetic leads
made with manganites or a substitutional transition metal impurity in a MnO
chain. We determined the region in parameter space where the impurity is empty,
half-filled or doubly-occupied and hence where it is magnetic or nonmagnetic.
The most important result is that we found, for a wide range of impurity
parameters and electron densities where the impurity is magnetic, a singlet
phase located between two saturated ferromagnetic phases which correspond
approximately to the empty and double-occupied impurity states. Transport
properties behave in general as expected as a function of the impurity
occupancy and they provide a test for a recently developed numerical approach
to compute the conductance. The results obtained could be in principle
reproduced experimentally in already existent related nanoscopic devices or in
impurity doped MnO nanotubes.
