Room temperature giant magnetoimpedance in polycrystalline La0.75Ba0.25MnO3

We report the magnetic field dependence of electrical impedance Z in polycrystalline La0.75Ba0.25MnO3 a function of frequency from f = 1 MHz to 1 GHz at room temperature. The magnetoimpedance [MI = ΔZ/Z(0) where ΔZ = Z(H)-Z(0)] is −37.5 % (-58.5%) at 1(10) MHz for H = 1.2 kOe, which far exceeds mere -1.15% dc magnetoresistance. As f increases above 10 MHz, MI decreases in magnitude and changes sign from negative to positive. The change in sign of MI results from the transition of a single peak at H = 0 to two peaks at H = ± Hp accompanied by a minimum at the origin. Hp shifts towards higher field with increasing frequency. The occurrence of giant radio-frequency magnetoimpedance is promising for low-field sensor applications.