  In order to model a spiral spin state in a thin film, we study a classical
Heisenberg model with open boundary conditions. With magnetic field applied in
the plane of the film, the spin state becomes ferromagnetic above a critical
field that increases with thickness $N$. For a given $N$, the spiral passes
through states with $n= n_0$ up to 0 complete periods in steps of 1. These
numerical results agree with earlier analytic results in the continuum limit
and help explain the susceptibility jumps observed in thin films.
