First-, second-, and infinite-order transitions in three-dimensional models with competing interactions

The ferromagnetic-modulated transition in the biaxial (m=2) XY Lifshitz-point model with p-fold anisotropy in spin space is studied via renormalization-group techniques in three dimensions. For sufficiently large p the transition is, respectively, first and second order at low and high temperatures; an infinite-order critical point separates the two regimes. © 1982 The American Physical Society.