Composition- and temperature-dependent magnetic structures of the layered manganites La2-2xSr1+2xMn2O7 (x=0.35 and 0.4)

Temperature-dependent neutron diffraction studies were performed on the ferromagnetic layered manganites La2-2xSr1+2xMn2O7 (x = 0.35 and 0.4), and,the detailed temperature variations of the crystal and the magnetic structures are reported. The ferromagnetic Mn-spins had temperature-dependent orientations. The spins were tilted towards the c-axis of the tetragonal unit cell, perpendicular to the perovskite layer at the onset of the ferromagnetic state and as the temperature was lowered gradually rotated to the ab-plane to tilting angles (theta) against the c-axis of 62(l)degrees and 65(2)degrees for the x = 0.35 and 0.4 compounds, respectively. A simple model based on crystal field theory is proposed to explain the variation of the tilting angle with the composition and the temperature of the compounds with 0.30<x<0.4.