Phase separation and microwave response of epitaxial and polycrystalline manganite films

Abstract

The resistance, magnetoresistance, and resistance response under microwave irradiation (f = 10 and 35 GHz) were measured for epitaxial and polycrystalline La0.67Ca0.33MnO3 and La0.67Sr0.33MnO3 thin films in the temperature range 78 divided by 300 K. The microwave induced resistance increase observed for the epitaxial films in a narrow temperature range below the ferromagnetic to paramagnetic transition temperature T-c certifies coexistence of low resistance (ferromagnetic) and high resistance (paramagnetic) regions in the manganites. Resistance of polycrystalline films decreased under microwave irradiation in a wide temperature range below T-c...