Abstract :
The current–voltage characteristics of several manganite systems like La 0.87 MnO 3 – ( Mn 2 O 3 ) 0.13 , La 0.60 Y 0.07 Ca 0.33 MnO 3 and Nd 0.55 Sm 0.3375 Sr 0.1125 MnO 3 show non-Ohmic behaviour at different temperatures. The onset voltage V 0 ( T ) at which conductance starts deviating from its zero-bias value Σ 0 ( T ) scales as V 0 ( T ) ∼ Σ 0 ( T ) x T with xT being the onset exponent. A detailed scaling analysis with these manganite systems reveal that the onset exponents xT are different in the paramagnetic insulating and ferromagnetic metallic phases. Besides, the magnitudes of xT are different in different manganite systems. Non-Ohmic conduction and the onset exponent are described with the help of inelastic multi-step tunneling model and scaling concepts.
