Spin-1/2 One-Dimensional Heisenberg Ferromagnet at Low-Temperature

Abstract

Using Bethe ansatz integral equations, we calculate the free energy and susceptibility of spin-1/2 one-dimensional Heisenberg ferromagnet (Remark: Graphics omitted.), (J<0) at T≥0.004|J|. We find that the free energy and susceptibility are expanded by \sqrtT⁄|J| at low temperature:
(Remark: Graphics omitted.)
The first term of free energy coincides with the spin wave calculation. The first term of susceptibility coincides with Fisher’s solution of classical Heisenberg Ferromagnet. We conclude α=−0.5 and γ=2.