Spin-½ Heisenberg Ferromagnet on Cubic Lattices: Analysis of Critical Properties by a Transformation Method

The high-temperature series expansions for the spin-½ Heisenberg ferromagnetic model on cubic lattices are analyzed by a transformation method. Evidence is presented suggesting that the susceptibility critical exponent ($\gamma$) and the gap parameter ($2\Delta$) are both smaller than the original estimates obtained by Padé approximant techniques. Specifically, we find that $\gamma =1.36\mathrm{}\pm 0.04$ and $2\Delta =3.50\mathrm{}\pm 0.20$. The error limits are to be taken as a reasonable confidence level rather than as a strict bound.