Calculation of finite temperature magnetic properties of clusters

The finite temperature magnetic properties of small clusters having N less than or equal to 6 atoms are determined in the framework of the single-band Hubbard model by using exact diagonalization methods and by taking into ac count both electronic and structural excitations. Results are given for the average magnetic moment < S > and for the spin correlation function < S-i. S-j>. The temperature dependence in weakly, intermediate, and strongly int eracting regimes is analyzed and the role of temperature-induced structural changes is discussed. (C) 2000 American Institute of Physics. [S0021-8979( 00)30308-5].