Study on magnetic ordering in (La, Nd, Sr)₂CuO₄

Spin structures of La_1.65Nd_0.35CuO₄, which undergoes a structural transition at T = T'₁ ∼ 80 K from the orthorhombic (Bmab) to another orthorhombic (Pccn) phase, have been studied by single crystal neutron diffraction and magnetization measurements. The Néel temperature T_N was found to be about 303 K. Above T'₁, the La₂CuO₄-type spin structure is observed. Below T' ₁, the observed intensities can be explained by the mixtures of the La₂CuO₄-type and La₂NiO₄-type spin structures with spin cantings. Search for the spin ordering in La_1.49Nd_0.39Sr_0.12CuO₄ has also been carried out in the low-temperature tetragonal (P4₂/ncm) phase, where the superconductivity is suppressed, but no evidence for the ordering has been observed.