Direct visualization of cubic to tetragonal phase transition in La0.2Sr0.8MnO3−δ using transmission electron microscopy

Structural phase transition studies employing low-temperature transmission electron microscopy (LT-TEM) and low-temperature x-ray diffraction (LT-XRD) have been carried out on wide-band La0.2Sr0.8MnO3−δ (δ=0.01) manganite. These studies reveal clear evidence of cubic to tetragonal phase transition occurring below 260 K in La0.2Sr0.8MnO3−δ (δ=0.01). TEM observations depict that cubic to tetragonal phase-transition results in formation of nanotwinned microstructure of the tetragonal phase. Formation of nanotwins has been attributed to orbital-orientation phase-separation leading to minimization of strain. The magnetic and electron transport measurements reveal that the structural phase transition is coupled with a canted C-type antiferromagnetic and semi-conductor to insulating phase transition.