Magnetic properties of Hubbard clusters: Non-collinear spins in 3-atom clusters

The ground-state magnetic properties of clusters with N = 3 atoms 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 the total energy and magnetic order, as a function of the Coulomb interaction strength U/t and number of electrons ν, are presented. For half-band filling an antiferromagnetic non-collinear spin arrangement is the most stable for the triangle structure. For ν = 2 and U/t ≥ 16.2, ν = 4 and U/t ≤ 2.3 the linear chain is the most stable structure. In particular, it is found that the inclusion of non-collinear spins improves in the Hartree-Fock ground-state energy as compared with collinear spins. Our results are compared and discussed with exact calculations.

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