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

Abstract

We have demonstrated Ru⁴⁺ induced colossal magnetoimpedance (MI) at room temperature in a ∼1 Tesla magnetic field with a pulsed laser deposited La_0.7Ca_0.3Mn_0.7Ru_0.3O₃ thin film. This composition showed a large negative ∼12% MI in the low frequency range (<5 MHz), a colossal positive MI > 120% in the intermediate frequency range (5 MHz to ∼13 MHz) and a negative MI in the high frequency range (∼13 MHz to 40 MHz) at room temperature. XAS data confirmed the predominant Ru valence state was 4+ in La_0.7Ca_0.3Mn_0.7Ru_0.3O₃. Ru⁴⁺ induced (i) charge carrier localization and (ii) reduced hole carrier density enhances the MI in this composition, which otherwise was not significant in mixed valences Mn³⁺/Mn⁴⁺ containing La_0.7Ca_0.3MnO₃ and Ru⁴⁺/Ru⁵⁺ and Mn³⁺/Mn⁴⁺ mixed valences containing Ru = 0.1 and Ru = 0.2 compositions in La_0.7Ca_0.3Mn_1−xRu_xO₃ (0 ≤ x ≤ 0.3) thin films.