Abstract

Anisotropic magnetic and transport properties as well as magnetic structures have been investigated for single crystals of bilayer manganites (La_1-zNd_z)_2-2xSr_1+2xMn₂O₇ as a function of doping level x and averaged ionic radius z of the rare-earth ion. We have derived a global magnetic phase diagram as a function of x and z. The ferromagnetic metallic state observed in La_1·2Sr_1·8Mn₂O₇ (x = 0· 4 and z = 0· 0) is replaced by a layered antiferromagnetic state beyond x ≥ 0·45. The phase diagram thus obtained is compared with that for the cubic manganites (La_1-zNd_z)_1-xSr_xMnO₃.