Functional-integral approach to the investigation of the spin-spiral   magnetic order and phase separation
  We investigate a two-dimensional single-band Hubbard model with a nearest-neighbor hopping. We treat a commensurate collinear order as well as incommensurate spiral magnetic phases at a finite temperature using a Hubbard-Stratonovich transformation with a two-field representation and solve this problem in a static approximation. We argue that temperature dramatically influence the collinear and spiral magnetic phases, phase separation in the vicinity of half-filling. The results imply a possible interpretation of unusual behavior of magnetic properties of single-layer cuprates. 
Anatoly Arzhnikov, Andrey Groshev
cond-mat.str-el