For the one-dimensional Ising model with a special incommensurate field, the ground-state magnetization as function of the field exhibits a staircase with an infinite number of almost exponentially decreasing steps. With increasing temperature, the steps get smoother and disappear successively. The specific heat resembles that of the Ising model with a constant field.

• Received 9 April 1984

DOI:https://doi.org/10.1103/PhysRevB.30.5190