Magnetic properties and ferromagnetic microstructures in Al-doped LaSrMnO

Mori, Shigeo*; Yoshidome, Kazuhiro*; Nagamine, Yuki*; Togawa, Yoshihiko*; Yoshii, Kenji  ; Takenaka, Koshi*

Doping effect on ferromagnetic (FM) properties in perovskite manganites LaSrMnO (x=0.175) were investigated by low-temperature Lorentz transmission electron microscopy (TEM), in combination with the conventional magnetic measurements. It is found that LaSrMnAlO exhibits a structural phase transition from the rhombohedral to orthorhombic structures at Ts116 K. During the rhombohedral-to-orthorhombic transition, the FM domain structures changed from the macroscopic FM domains to the FM ones with the wavy stripe pattern. The ac magnetic measurements also revealed that LaSrMnAlO shows unconventional magnetic behaviour at low temperature below 65 K. Partial substitution of non-magnetic Al for Mn has some influence on magnetic ordering and double-exchange interaction, which should induce insulator behaviour in the orthorhombic phase.