Magnetic and electronic phase diagram of a ferromagnetic La 0.6Pb 0.4Mn 1− xRu xO 3 series

Abstract

The nature of the magnetic interactions between Mn and Ru in La 0.6Pb 0.4Mn 1− x Ru x O 3 where 0⩽ x⩽1 have been explored by magnetic and transport measurements. The ferromagnetic Curie temperature decreases from 345 K to 105 K for x=0.0 up to x=0.9, while the metal–insulator transition is accompanied by the Curie temperature up to x=0.4. These results indicate that double exchange ferromagnetic interaction is predominating over the superexchange ferromagnetic and superexchange anti-ferromagnetic interactions up to x=0.4, in contrast to the other 3d dopant elements such as Ti, Cr, Fe, Co, Ni and Cu. We attribute the long-range ferromagnetic interaction and a dominant DE process to the variable valence states of Ru (Ru 4+/Ru 5+) as inferred from the X-ray absorption spectroscopic studies (XAS). The similar e g parentage of Ru 5+ (t 2g 3e g 0) to Mn 4+ (t 2g 3e g 0) provides a template for the Mn 3+ (t 2g 3e g 1) center to prolong the double exchange interaction using e g electron itinerancy.