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 generated in this material by a very slight canting of the Cu moments from a perfect antiferromagnetic structure. This canting enables the inspection of the magnetic state of the Cu sublattice by pure magnetic methods. The critical exponents of the transition are calculated, γ=1.32(2), β=0.34(1). Nevertheless, a rapid evolution of β to a 2D XY behavior is observed below 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 point due to the effect of the interlayer interaction along the c-axis.