Nonlinear transport in nanoscale phase separated colossal magnetoresistive oxide thin films

transport in nanoscale phase separated colossal magnetoresistive oxide thin films" (2014). Preparation of rare-earth manganite-oxide thin films by metalorganic aerosol deposition technique Appl. We report a study of the I-V characteristics of 2.5–5.4 nm epitaxial La 1Àx Sr x MnO 3 (x ¼ 0.33 and 0.5) and La 0.7 Ca 0.3 MnO 3 thin films. While La 0.67 Sr 0.33 MnO 3 films exhibit linear conduction over the entire temperature and magnetic field ranges investigated, we observe a strong correlation between the linearity of the I-V relation and the metal-insulator transition in highly phase separated La 0.5 Sr 0.5 MnO 3 and La 0.7 Ca 0.3 MnO 3 films. Linear I-V behavior has been observed in the high temperature paramagnetic insulating phase, and an additional current term proportional to V a (a ¼ 1.5–2.8) starts to develop below the metal-insulator transition temperature T MI , with the onset temperature of the nonlinearity increasing in magnetic field as T MI increases. The exponent a increases with decreasing temperature and increasing magnetic field and is significantly enhanced in ultrathin films with thicknesses close to that of the electrically dead layer. We attribute the origin of the nonlinearity to transport through the nanoscale coexisting metallic and insulating regions. Our results suggest that phase separation is not fully quenched even at low temperatures and high magnetic fields.