A new low-temperature anomalous magnetism at about 29 K for the oxygen
-doped (Eu1-xYx)(2)CuO4 and Sm2CuO4, prepared under high pressure, has
been investigated. This anomaly originated from different mechanisms
to weak ferromagnetism (WF) behavior of T' phase, and should be assign
ed to the ferromagnetic clusters formed by doped holes.