text: FIG. 4: (color online) Thermodynamic quantities obtained for 
  thickness n = 8 in the temperature range 0-150 K. Colors and 
  symbols as in Fig. 2. (a): speciﬁc heat; (b): chirality order 
  parameter. (c): susceptibility χκ. (d): Binder cumulant for 
  κ. 
  
  FIG. 3: (color online) Binder cumulants at thickness n = 
  16, colors as in Fig. 2. (a): Binder cumulant for the order 
  parameter deﬁned in Eq. (3). (b): Binder cumulant extracted 
  from the integral of the structure factor (see Sec. II). Inset: 
  structure factor for L = 64 between T = 131 K (upper curve) 
  and T = 140 K (lower), with 1 K temperature step. 
  
  133.1(3) K (see Fig. 3b). The crossing points of the 
  Binder’s cumulants of the helical order parameter imme- 
  diately appear to be located, within the error bars, at the 
  same temperature of those for the average magnetization 
  previously discussed. In addition, it is worthwhile to ob- 
  serve that the peak evolution of S(0, 0, qz), in particular 
  close to TN (16) (inset of Fig. 3b), displays the typical 
  behaviour expected for an helical structure. We can thus 
  conclude that for n = 16, as it is commonly observed 
  in bulk samples, the establishment of the in-plane order 
  coincides with onset of the perpendicular helical arrange- 
  ment at TN (16). However, due to helix distortion in the 
  surface regions, the maximum of S(0, 0, qz) stabilizes at 
  values of qz sensibly smaller (e.g. Qz(TN (16)) ≈ 16◦, 
  and Qz(T = 10K) ≈ 28◦) with respect to the bulk one 
  (QHo 
  
  III. RESULTS 