MAGNETIC AND ELECTRONIC-PROPERTIES OF SUBSTITUTIONAL FEN CLUSTER IMPURITIES IN CR - TRANSITION FROM ANTIFERROMAGNETIC TO FERROMAGNETIC FEN

We present a study of the magnetic and electronic properties of Fe(N) clusters embedded in antiferromagnetic bcc Cr. The spin-polarized char ge distribution is determined self-consistently by solving a realistic spd-band model Hamiltonian including intra-atomic Coulomb interaction s in the unrestricted Hartree-Fock approximation. For all the studied clusters (N less-than-or-equal-to 51), the local magnetic moments at F e atoms close to the Fe-Cr interface, as well as the average magnetic moment of the Fe(N) impurity, are reduced with respect to the Fe bulk magnetization. The magnetic order within Fe(N) changes from antiferrom agneticlike to ferromagneticlike with increasing cluster size. The cal culated critical size for this transition is N(c) congruent-to 6. Resu lts for the spatial distribution of the magnetic moments and for the l ocal electronic densities of states are given for different N. The rol e of the structural and chemical local environment of the atoms on the electronic and magnetic properties is discussed, and our results are compared with those found for Fe/Cr multilayers. Some of the implicati ons of the present study for magnetic alloys and ferromagnetic cluster s on surfaces are pointed out.