Double magnetic transition in Pr0.5Sr0.5CoO3 -: art. no. 024427

We report studies of polycrystalline samples of the metallic ferromagnet Pr0.5Sr0.5CoO3 through measurements of the magnetization, ac magnetic susceptibility, resistivity, and specific heat. We find an unusual anomaly around T-A=120 K, much below the ferromagnetic transition (T-C=226+/-2 K). The anomaly is manifested in field cooled magnetization as a downward step in low fields (Hless than or equal to0.01 T) but is transformed into an upward step for Hgreater than or equal to0.05 T. The anomaly cannot be easily attributed to antiferromagnetic ordering, but may correspond to a second ferromagnetic transition or an alteration of the ferromagnetic state associated with orbital ordering.