MAGNETIC-PROPERTIES OF ND2CUO4-TYPE Y2CUO4, DY2CUO4, HO2CUO4, ER2CUO4, TM2CUO4 SYNTHESIZED UNDER HIGH-PRESSURE - WEAK FERROMAGNETISM OF Y2CUO4

Magnetization of R2CuO4 (R=Y, Dy, Ho, Er, Tm) crystallizing in the Nd2CuO4-type (T) structure has been measured between 4 and 300 K. In Y2CuO4 antiferromagnetic ordering of Cu2+ spins at 260 K has been detected clearly, without being interfered with by the paramagnetic contribution of rare-earth elements as in the other compositions. Weak ferromagnetic behavior with a moment of 9×10-4 B/Cu accompanies the antiferromagnetic transition. Dy3+, Ho3+, Er3+, and Tm3+ ions obey the Curie-Weiss law at relatively high temperatures, and the effective moments are in good agreement with the values anticipated from their lowest multiplet levels. Various types of deviations from the law occur at low temperatures. Specifically, a sharp kink possibly suggesting antiferromagnetic ordering of the Dy3+ moments has been found at 7 K. Anomalies around 200 K for Ho2CuO4 and Er2CuO4 reflect the weak ferromagnetic contribution of the CuO2 lattice. © 1990 The American Physical Society.