Lorentz transmission electron microscopy observation of magnetic domains in La0.825Sr0.175(Mn,Al)O3.

Nonmagnetic Al substitution effect on the stability of a ferromagnetic (FM) metallic state in double-exchange manganite, La_0.825Sr_0.175MnO₃, was investigated by Lorentz transmission electron microscopy (TEM), in combination with magnetic measurements. Both FM transition temperature (Tc) and the rhombohedral-to-orthorhombic (R-to-O) transition temperature (Ts) decreased by a few percent of Al substitution. An in situ Lorentz TEM observation revealed that drastic change of the FM domain structure took place through the R-to-O structural transition. The magnetization decreased slightly at Ts and characteristic spin-glass state is realized in the low-temperature region below Ts. [ABSTRACT FROM AUTHOR]