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Noncollinear cluster magnetism in the framework of the Hubbard model

Miguel A. Ojeda·J. Dorantes-Davila·G. M. Pastor
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Abstract

Noncollinear magnetic states in clusters are studied by using the single-band Hubbard Hamiltonian. The unrestricted Hartree-Fock (UHF) approximation is considered without imposing any symmetry constraints neither to the size or orientation of the local magnetic moments $<\vec S_l>$ nor to the local charge densities $ $. A variety of qualitatively different selfconsistent solutions is obtained as a function of cluster size, structure, number of valence electrons $ν$ and Coulomb interaction strength $U/t$. This includes inhomogeneous density distributions, paramagnetic solutions, magnetic solutions with collinear moments and noncollinear spin arrangements that show complex antiferromagnetic and ferromagnetic-like orders. The environment dependence of the magnetic properties is analyzed giving emphasis to the effects of antiferromagnetic frustrations in compact structures close to half-band filling. Electron correlation effects are quantified by comparing UHF and exact results for the local magnetic moments, total spin, spin-correlation functions and structural stability of 13-atom clusters. Goals and limitations of the present noncollinear approach are discussed.

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Miguel A. Ojeda, J. Dorantes-Davila, G. M. Pastor. 1999-03-21. Noncollinear cluster magnetism in the framework of the Hubbard model. https://doi.org/10.1103/physrevb.60.6121

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