  The magnetic response of irreversible type-II superconductor slabs subjected
to in-plane rotating magnetic field is investigated by applying the circular,
elliptic, extended-elliptic, and rectangular flux-line-cutting critical-state
models. Specifically, the models have been applied to explain experiments on a
PbBi rotating disk in a fixed magnetic field ${\bm H}_a$, parallel to the flat
surfaces. Here, we have exploited the equivalency of the experimental situation
with that of a fixed disk under the action of a parallel magnetic field,
rotating in the opposite sense. The effect of both the magnitude $H_a$ of the
applied magnetic field and its angle of rotation $\alpha_s $ upon the
magnetization of the superconductor sample is analyzed. When $H_a$ is smaller
than the penetration field $H_P$, the magnetization components, parallel and
perpendicular to ${\bm H_a}$, oscillate with increasing the rotation angle. On
the other hand, if the magnitude of the applied field, $H_a$, is larger than
$H_P$, both magnetization components become constant functions of $\alpha_s$ at
large rotation angles. The evolution of the magnetic induction profiles inside
the superconductor is also studied.
