Observation of spin reorientation in layered manganites La1.2Sr1.8(Mn1−yRuy)2O7 (0.0⩽y⩽0.2) by Lorentz transmission electron microscopy

Abstract The effect of Ru substitution for Mn in bilayered oxides La 1.2 Sr 1.8 (Mn 1− y Ru y ) 2 O 7 ( 0 ⩽ y ⩽ 0.2 ) was investigated by magnetization measurements and low-temperature Lorentz transmission electron microscopy. It was found that the magnetic anisotropy is controlled by the Ru content y and temperature T . The easy axis changes from 〈1 1 0〉 for the y = 0 crystal to the c -axis for y = 0.2 , and it rotates away from the c- axis for the y = 0.05 and y = 0.07 crystals with decreasing temperature. Furthermore, maze-shaped magnetic domain structures were observed in the (0 0 1) thin crystals with 0.05 ⩽ y ⩽ 0.2 . Changes in domain size and structure indicate that the uniaxial magnetic anisotropy becomes stronger as Ru content y increases.