OCCURRENCE OF WEAK FERROMAGNETISM IN T'-(R1-XYX)2CUO4 (R = SM AND EU)

Results for the temperature dependence of the magnetic susceptibility for Gd2CuO4, (Sm1-xYx)2CuO4, and (Eu1-xYx)2CuO4 with various Y concent rations are reported. The magnetic anomalies that occurred at T(N)(Cu) approximately 285 K and T(m) approximately 20 K in Gd2CuO4, are not o bserved in Sm2CuO4 or Eu2CuO4, and are seen in (Sm1-xYx)2CuO4 and (Eu1 -xYx)2CuO4 with x greater-than-or-equal-to 0.3 and x greater-than-or-e qual-to 0.05,respectively. It is found that the transition temperature s T(N)(Cu) and T(m) and the magnitudes of anomalies are very sensitive to Y substitution. Thus, the effect of small ionic radius for Gd play s a much more important role than its large moment on the anomalous ma gnetic properties of Gd2CuO4. This also provides clear evidence that t he magnetic anomalies in Gd2CuO4 are due to weak ferromagnetism in the Cu-O plane resulting from the too small ionic radius of Gd, which ind uces a lattice distortion in the T' structure.