Anisotropic magnetic, magnetoresistance, and electrotransport properties of GdBaCo2O5.5 single crystals -: art. no. 214421

Single crystals of GdBaCo2O5.5 layered perovskites have been grown from a flux melt of Gd2O3-BaO-CoO oxides. Magnetic data showed that the GdBaCo2O5.5 single crystals exhibit a magnetic phase transition from an antiferromagnetic state to a ferromagnetic one with spontaneous magnetization around 0.41 mu(B) per Co ion at T(i)similar to160 K. Direction of spontaneous magnetic moment coincides with either the a or b axis. It is assumed that Co3+ ions adopt low- and intermediate-spin states in the ratio of 1:1. The giant magnetoresistance effect connected closely with a spontaneous magnetization appearance shows a strong anisotropic that is behavior consistent with the anisotropy of magnetic properties. On the basis of electrical resistivity data the quasi-two-dimensional character of conductivity, above the metal-insulator transition temperature T(MI)similar to370 K, was assumed.