  We have performed DC and AC magnetization measurements for the rare-earth
magnetic alloy systems Gd_{0.62}Y_{0.38}, Tb_{0.86}Y_{0.14}, and
Dy_{0.97}Y_{0.03}. These materials commonly exhibit a proper helical magnetic
structure, and ferromagnetic structure at lower temperatures.In all of these
materials, a difference between zero-field-cooled (ZFC) magnetization and
field-cooled (FC) magnetization and a hysteresis loop in the M-H curve have
been observed in the helimagnetic phases. The non-equilibrium behavior is
possibly caused by a common nature, e. g., chiral domain structures. In
addition to the above behavior, strong non-linearity of the magnetization and
slow spin dynamics have been observed around the N'eel temperature only in
Gd$_{0.62}$Y$_{0.38}$. The spin-glass like behavior observed in
Gd_{0.62}Y_{0.38} could be related to a novel glassy state such as a
helical-glass state.
