Magnetic properties of 3d transition-metal nanostructures: Cr and V clusters embedded in bulk Fe

The magnetic and electronic properties of Cr-N and V-N clusters embedded in Fe are determined by using a realistic spd-band Hubbard-like model Hamiltonian. The spin-density distribution is calculated self-consistently in the unrestricted Hartree-Fock approximation. The local magnetic moments mu(i) and the densities of electronic states rho(i)(epsilon) are obtained at different atoms i of the cluster and of the surrounding Fe matrix. For all the studied clusters (N less than or equal to 51 atoms) the interface magnetic coupling between cluster and matrix moments is antiparallel. The mu(i) of Cr or V atoms at the interface are enhanced by the presence of Fe atoms in their first-nearest-neighbor shell. In most cases the Fe moments close to the cluster are slightly reduced. In CrN the interface mu(i) are often much larger than the Cr bulk moments [e.g., mu(i) = -1.30 mu(B) for Cr-4 in Fe]. In V-N large mu(i) are induced which decrease as N increases or as we move from the interface to the interior of the cluster [e.g., mu(i) = -1.29 mu(B) for V-4 in Fe]. A remarkable interplay between the antiferromagnetism of Cr, the paramagnetism of V, and the ferromagnetism of Fe is obtained. The magnetic order within Cr-N (V-N) changes from ferromagnetic to antiferromagnetic for N greater than or equal to 9 (N greater than or equal to 6). This results in an interesting size dependence of the cluster electronic density of states. [S0163-1829(98)02741-6].