Two-dimensional antiferromagnetic correlations in an La1.4Sr1.6(Mn0.9Co0.1)(2)O-7 single crystal

The temperature and field dependences of the magnetization, the electrical resistivity, and the magnetostriction of bilayer lanthanum manganite La_1.4Sr_1.6Mn₂O₇ single crystals and cobalt-doped La_1.4Sr_1.6(Mn_0.9Cu_0.1)₂O₇ are measured. The magnetostriction of the cobalt-doped compound increases as compared to the initial La_1.4Sr_1.6Mn₂O₇ compound, and the magnetization and the magnetoresistance of the former compound change substantially. Powder and single-crystal neutron diffraction patterns are used to detect ferromagnetic ordering in La_1.4Sr_1.6(Mn_0.9Co_0.1)₂O₇ at a temperature below T_C ~ 45(2) K, and this ordering coexists with antiferromagnetic correlations, which develop at temperatures below T_C ~ 80(5) K.