Effect of Ru–Mn redox interactions on the hole carrier density in pulsed electron deposited La_1−xPb_xMn_0.8Ru_0.2O₃(0.2≤x≤0.4) thin films

Abstract

Pulsed electron deposited thin films of Ru substituted La(1-x)Pb(x)Mn(0.8)Ru(0.2)O(3) (0.2≤x≤0.4) show an increase in the magneto-resistance ratio by ∼5-15% at the respective metal to insulator transition (T(MIT)) temperature when compared to the parent La(0.6)Pb(0.4)MnO(3) thin film. A systematic decrease in T(MIT) is observed from ∼310 to ∼260 K when the hole (Pb) concentration varies from 40 to 20% with constant 20% Ru substitution at the Mn site. The x-ray rocking curve and high-resolution transmission electron microscopy (HRTEM) images of the thin films suggest that Ru occupies the Mn site and shows epitaxial growth of the films on the LaAlO(3) (LAO) substrate. Transport and magneto-resistive properties show that Ru substitution maintains a considerable hole carrier density (due to Mn(4+):t(2g)(3)e(g)(0)/Ru(5+):t(2g)(3)e(g)(0)) even for La(0.8)Pb(0.2)Mn(0.8)Ru(0.2)O(3) (8282) composition, which influences the double exchange interactions.

Ru4+ induced colossal magnetoimpedance in Ru doped perovskite manganite at room temperature

“…T MIT and T c may have originated predominantly from the chemical pressure effects of the cationic size of the Ca ion, deficiency of the hole carrier density that brings in charge carrier localization due to the random magnetic potential effects, as was demonstrated for the Ru substituted samples. 35,36 Fig. 3(i and ii) and 4(i and ii) show the impedance and magneto impedance of La 0.7 Ca 0.3 Mn 1Àx Ru x O 3 (0 r x r 0.3) thin films.…”

“…It was found that in Ru substituted manganite, wherein the Ru concentration was 420%, those compositions showed a charge carrier localization effect. 35,36 This effect arises because (i) hole carrier density being decreased due to the Ru 4+ (ii) in the presence of the Ru 4+ valence state, the e g electron is not able to hop from Mn 3+ . In Fig.…”