Magnetic order and weak ferromagnetic transition in Gd2CuO4

The weak ferromagnetic transition of T-'-phase Gd2CuO4 single crystals has been studied by dc-magnetization measurements. Weak ferromagnetism is gener ated in this material by a very slight canting of the Cu moments from a per fect antiferromagnetic structure. This canting enables the inspection of th e magnetic state of the Cu sublattice by pure magnetic methods. The critica l exponents of the transition are calculated, gamma=1.32(2), beta=0.34(1). Nevertheless, a rapid evolution of beta to a 2D XY behavior is observed bel ow the critical temperature. It is interpreted as evidence of a transition in the 2D system, namely CuO2 planes, that behave as 3D at the critical poi nt due to the effect of the interlayer interaction along the c-axis. (C) 20 00 American Institute of Physics. [S0021-8979(00)76208-6].