X-ray diffraction, electrical and magnetic studies of solid solution La0.6Sr0.4MnO3-delta square(delta) (0.0 <=delta <= 0.2)

Nonstoichiometric substituted lanthanum manganite powder has been synthesiz ed by solid state reaction method. X-ray diffraction shows that the materia l exists in single phase having a perovskite structure. A structural phase transition separating a rhombohedral phase and an orthorhombic phase was Ob served at the rate delta approximate to 0.127 corresponding to a Mn3+ conce ntration of about 85%. The material is ferromagnetic for 0 less than or equ al to delta less than or equal to 0.127 and antiferromagnetic for 0.15 less than or equal to delta less than or equal to 0.20. The Curie temperature i s very sensitive to the presence of vacancies. The investigation of electri cal properties shows metallic behavior at low temperature for delta less th an or equal to 0.10 and as insulator for 0.127 less than or equal to delta less than or equal to 0.20. The variation of activation energies with the r ate of vacancies has been investigated.