Critical behaviour at a field-induced magnetic phase transition at T = 0

Abstract

We study the critical behaviour at the field-induced phase transition in an anisotropic ferromagnet at the magnetic displacive limit T = 0, H = H K . The critical behaviour of a classical magnet is shown to be equivalent to that of a classical lattice-dynamical system at the displacive limit of a structural phase transition. We also report exact results for a quantum magnet with infinite-range interactions, for the transverse Ising model and the anisotropic XY -chain, and for the spin-wave theory of a uniaxial ferromagnet.