Breakdown of Scaling in the Spin-1/2 Heisenberg Ferromagnet

The problem of the critical behavior of the spin‐1/2 Heisenberg ferromagnetic chain has challenged many research workers since 1964. We discuss the critical exponents α and γ recently determined by Schlottmann and by Takahashi and Yamada in the context of previously known T c =0 critical properties of the 1D s=1/2 X X Z model and the classical Heisenberg model, and we comment on the manifest breakdown of scaling in the s=1/2 Heisenberg ferromagnet