Anomalous magnetic diffuse scattering in a bilayer manganite La 2-2x Sr 1+2x Mn 2 O 7 ( x =0.45)

We performed neutron-diffraction measurements on single crystals of La2-2xSr1+2xMn2O7. For x=0.45, in an intermediate phase (TC<T<TN), an antiferromagnetic (AFM) correlation gives rise to a diffuse signal along c with a period of 1/zo (zo∼0.2; the distance of Mn ions within a bilayer along c). Below TC, however, the period of the diffuse signal changes due to the appearance of a canted AFM structure. These results indicate that a phase separation does not occur between a ferromagnetic (FM) and an AFM spin correlation along c.