Magnetoimpedance effect in manganite La 2/3Ba 1/3MnO 3 at various temperatures

Abstract

In the present work, the magnetoimpedance (MI) effect for the manganite La 2/3Ba 1/3MnO 3 at various temperatures was reported. At a lower frequency such as f=100 kHz, the metal–insulator transition temperature T MI deduced from the peak in the temperature dependence of the AC impedance Z is very close to the value obtained from the DC resistance case, meanwhile there exists a peak of the MI Δ Z/ Z 0 near the T MI. Similar to the case of DC colossal magnetoresistance effect, the T MI in MI effect can be shifted to a high temperature under application of a DC field. At a higher frequency such as f=23 MHz, a valley of the impedance Z dominated by the term of the reactance X occurs at the T MI, which can be moved by a field. The impedance Z increases with increasing AC frequency due to the skin effect. The variation of the resistance R with AC frequency strongly depends on the temperature. Below the T MI, the R increases with frequency. Above the T MI, with increasing AC frequency the R increases slightly at first, undergoes a valley, and finally increases again. Our present results imply that the interplay between the double-exchange effect and the electron–phonon coupling may also involve in the MI effect of the manganites, in addition to the variation of penetration depth via the permeability and conductivity under the application of DC fields.