Phase Separation and Microwave Response of Epitaxial and Polycrystalline Manganite Films
S. Asmontas a,d , A. Abrutis b , J. Gradauskas a,c A. Lucun a , A. Oginskis a , V. Plausinaitiene a,b , A. Suziedelis a,c and B. Vengalis a,c
a Semiconductor Physics Institute, A. Gostauto 11, 2600 Vilnius, Lithuania
b Department of General and Inorganic Chemistry, Vilnius University Naugarduko 24, 2006 Vilnius, Lithuania
c Vilnius Gediminas Technical University, Sauletekio al. 11, 2040 Vilnius, Lithuania
d KTU Panevezys Institute, Klaipedos 3, 5319 Panevezys, Lithuania
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The resistance, magnetoresistance, and resistance response under microwave irradiation (f=10 and 35GHz) were measured for epitaxial and polycrystalline La 0.67 Ca 0.33 MnO 3 and La 0.67 Sr 0.33 MnO 3 thin films in the temperature range 78300K. 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 . The effect was explained in terms of microwave assisted hopping of carriers in high resistance regions formed at grain boundaries of the polycrystalline films.
DOI: 10.12693/APhysPolA.105.141
PACS numbers: 75.47.Gk, 75.47.Lx, 07.57.Kp