Electronic phase transition and ferromagnetic ordering in LaMn0.95−xRuxO3 (x≤0.4)

Ruthenium doped B-site deficient compound, LaMn0.95−xRuxO3, where 0≤x≤0.4 shows a ferromagnetic metal (x<0.1) to insulator (for x>0.1) transition involving rhombohedral to orthorhombic symmetry change. The ferromagnetic metallic behavior is sustained by a double exchange mediated process, while for x>0.1 a superexchange ferromagnetic interaction is observed. The conduction mechanism in the paramagnetic state for all the compounds is dominated by the 3D-variable range hopping type. The charge carrier localization length, ξ decreases from 2.88 Å at x=0.0 to 1.64 Å for x=0.4. The unusual ferromagnetic interaction between Mn and Ru is explained based on the mixed valence effect.