bulk behaviour, with the single planes ordering tempera-
ture coinciding with the helical phase transition one;ii)
intermediate thickness, 6 ≤ n ≲ 15, where the tempera-
ture corresponding to the onset of in-plane order, TC (n),
is still ≃ T Ho
N , but where the helical/fan arrangement sta-
bilizes only below a ﬁnite temperature TN (n) < T C (n);
iii) low thickness,1 ≤ n ≤ 5, where TC (n) ≲ T Ho
N but no
fan phase is present at any temperature.
The observed behaviour in region iii) can be reason-
ably attributed to the decreasing relevance of the con-
tribution to the total energy of the system coming from
the competitive interactions among NNN planes as the
ﬁlm thickness decreases; moreover, the thinness of the