  It is unexpected that a spin-glass transition, which generally occurs only in
the system with some form of disorder, was observed in the ThCr2Si2-type
compound PrAu2Si2 at a temperature of ~3 K. This puzzling phenomenon was later
explained based on a novel dynamic frustration model that does not involve
static disorder. We present the results of re-verification of the reported
spin-glass behaviors by measuring the physical properties of three
polycrystalline PrAu2Si2 samples annealed under different conditions. Indeed,
in the sample annealed at 827 C for one week, a spin-glass transition does
occur at a temperature of Tf=2.8 K as that reported previously in the
literature. However, it is newly found that the spin-glass effect is actually
more pronounced in the as-cast sample, and almost completely disappears in the
well-annealed (at 850 C for 4 weeks) sample. The apparent sample dependence of
the magnetic characteristics of PrAu2Si2 is discussed by comparing it with
similar phenomena observed in the isomorphic compounds URh2Ge2 and CeAu2Si2.
Our experimental results strongly suggest that the spin-glass behavior observed
in the as cast and insufficient annealed samples is most likely due to the
presence of small amount of crystalline impurities and/or partial site disorder
on the Au and Si sublattices, and thus is not the inherent characteristic of
ideal ThCr2Si2-type PrAu2Si2. The perfectly ordered PrAu2Si2 should be regarded
as a paramagnetic system with obvious crystal-field effects.
