Unusual Substitutional Properties of Ru in the La0.7 Sr0.3Mn1–xRuxO3 System

La 0.7 Sr 0.3 Mn 1– x Ru x O 3 , 0 ≤ x ≤ 0.2 samples were prepared both in bulk and thin film formed using pulsed laser deposition. Magnetization measurements of bulk samples indicate a marginal decrease in T c from 366 to 335 K up to 15% Ru substitution in Mn site. X-ray diffraction of the ·100Ò oriented epitaxial films indicate a monotonic increase in the lattice parameter with Ru doping. The magnetoresistive behavior of the Ru substituted films are comparable with the parent La 0.7 Sr 0.3 MnO 3 films. Unlike other elemental substitution in Mn sites, the effect of Ru to stabilize magnetic ordering at elevated temperatures is exceptional.