Low temperature irreversibilities in the magnetothermal behavior of Gd2CuO4

The detailed investigation of the low temperature magnetic properties of Gd2CuO4 reveals the irreversible temperature behavior of the de magnetization and ac susceptibility that is associated with the presence of magnetic anomalies inbetween T-N(Gd) = 6.6 K and T-1 approximate to 20 K. Observed hysteresis is centered around 8 K-the temperature of the sudden drop in the magnetization that corresponds to the temperature of reorientation-type magnetic phase transition in the Cu sublattice, The significant irreversibility has also been found in the temperature range of the magnetic anomaly at T-1 approximate to 20 K. Following the theoretical model of the low temperature magnetic interactions proposed in Vitebsky et al. [Fiz. Niz. Temp. 20, 25 (1994)], the irreversible behavior around T-1 can be qualitatively understood assuming the existence of the magnetic clusters in the form of groups of Gd-Cu-Gd sandwiches. Comparing the results obtained for quenched and slowly cooled samples it can be concluded that the long distance coherence, presumably of the oxygen displacements in the crystal structure, is the predominant factor determining the low temperature magnetic behavior of the system. (C) 1998 American Institute of Physics. [S0021-8979(98)03819-5].