Competing A‐site and B‐site doping effects on magneto‐transport of RE_0.55 Sr_0.45 Mn_1−x Ru_x O₃ manganites in the vicinity of the SGI and FMM border

Abstract

Competing effects of the A—site and B—site doping on the magneto—transport have been investigated in RE0.55Sr0.45Mn1−xRuxO3 (0 ≤ x ≤ 0.25) manganites with RE (A—site) = GdySm1−y (0 ≤ y ≤ 1). The Ru (B—site)‐free system is a ferromagnetic metal (FMM) for y ≤ 0.5 and a spin—glass insulator (SGI) for y > 0.5. For y ≤ 0.5, Ru improves the metallicity compared to the Ru—undoped system. For y > 0.5, Ru—doping induces a transition from the SGI to FMM state, above a percolation threshold which depends strongly on the A—site substitution. Interestingly, irrespective of the A—site doping level y, the percolation is suppressed when the Ru concentration x exceeds ∼16% to 18%.