Magnetic phase diagram of double-layered La2-2xCa1+2xMn2O7 mangamte

Double-layered manganite La2-2xCa1+2xMn2O7 have been synthesized for compositions 'x' = 0.0, 0.1, 0.2, 0.3, 0.4 and 0.5 by solid state reaction method. From X-ray diffraction study, their crystal structures were found to be tetragonal perovskite with lattice parameters decreasing with increasing 'x'. The decreasing lattice parameters affect the balance between in-plane, intra-bilayer and interbilayer exchange interactions, which is reflected on magnetotransport properties. The metal-to-insulator transition temperature is found to vary with composition and peaked around 'x' = 0.3. From ac-susceptibility study, 2D-ferromagnetic ordering was observed at higher temperatures for all compositions whereas 3D-ferromagnetic ordering was observed at quite low temperatures. In low-temperature region, decreasing susceptibility shows antiferromagnetic state for all compositions. On the basis of electrical and magnetic properties, a magnetic phase diagram is given. (c) 2006 Elsevier Ltd. All rights reserved.