Influence of length and measurement geometry on magnetoimpedance in La0.7Sr0.3MnO3

We show that ac magnetoresistance at room temperature in La0.7Sr0.3MnO3 is extremely high (= 47% in H = 100 mT, f = 3-5 MHz), and magnetic field dependence of reactance exhibits a double peak behavior. However, magnitudes of the ac magnetoresistance and magnetoreactance for a fixed length of the sample (li) decrease with decreasing separation (lv) between voltage probes unlike the dc magnetoresistance. On the contrary, change in li has a negligible influence on magnetoimpedance when lv is fixed. Our results indicate that high frequency electrical transport is sensitive to local variations in the magnetic permeability.