Magnetic properties of Hubbard clusters: Noncollinear spins in N-atom clusters

The ground-state magnetic properties of clusters with N-atomic sites are studied by solving the single-band Hubbard Hamiltonian in the unrestricted Hartree-Fock approximation. Three-dimensional arrangements of spins are considered in the solution. Results for stability and magnetic order, as a function of the Coulomb interaction strength U/t, and number of electrons ν, are presented for all the clusters with N=3, 4, and for the set of N=13 fcc-, hcp-, icosahedral-. and bcc-like clusters. In most cases, for band fillings (ν) close to half-band |νlN- 1|≤0.2-0.4. it is found that the antiferromagneticlike noncollinear spin solutions yield the smallest energy for U/t larger than a critical value (0<(U/t)c≤6). © 1997 American Institute of Physics.

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