Giant magnetoimpedance and colossal magnetoresistance in La0.75Sr0.25MnO3 at room temperature

The impedance as well as the resistance and reactance of the La0.75Sr0.25MnO3 manganite increase with increasing ac frequency due to the skin effect of the metal state below Curie temperature. The manganite La0.75Sr0.25MnO3 shows not only the colossal magnetoresistance effect but also the giant magnetoimpedance effect. For the giant magnetoimpedance, the magnetic field influences the impedance by affecting the penetration depth via the transverse permeability, whereas for the colossal magnetoresistance the magnetic field tends to align the local spins, leading to the decrease of the dc resistance via the interplay between a strong electron-phonon coupling and the double exchange effect of spin alignment on electron kinetic energy. (C) 2002 American Institute of Physics.