  Detailed magnetization and magneto-transport measurements studies are carried
out to unearth the anomalous magnetism of Pr in PrCoAsO compound. The studied
PrCoAsO sample is single phase and crystallized in the tetragonal structure
with space group P4/nmm in analogy of ZrCuSiAs type compounds. Detailed
magnetization measurements showed that Co moments in PrCoAsO exhibit weakly
itinerant ferromagnetic Co spins ordering at below 80 K with a small magnetic
moments of 0.12 muB/f.u. High temperatures Curie-Weiss fit, resulted in
effective paramagnetic moment mueff (exp) of 5.91 muB/f.u., which can be
theoretically assigned to 3d Co (3.88 muB) and 4f Pr (3.58 muB). Further, a
positive Curie- Weiss temperature of 136 K is seen, indicating predominant
ferromagnetic interactions in PrCoAsO. Detailed transport measurements showed
that PrCoAsO exhibit metallic behavior and negative magneto-resistance below
ferro-magnetically (FM) ordered state. Surprisingly, the situation of PrCoAsO
is similar to non magnetic La containing LaCoAsO and strikingly different than
that as reported for magnetic Nd, Sm and Gd i.e., (Nd/Sm/Gd)CoAsO. The magnetic
behavior of PrCoAsO being closed to LaCoAsO and strikingly different to that of
(Nd/Sm/Gd)CoAsO is unusual.
