A 'p-n' diode with hole and electron-doped lanthanum manganite

The hole-doped manganite La0.7Ca0.3MnO3 and the electron-doped manganite La0.7Ce0.3MnO3 undergo an insulator to metal transition at around 250 K, above which both behave as a polaronic semiconductor. We have successfully fabricated an epitaxial trilayer (La0.7Ca0.3MnO3/SrTiO3/La0.7Ce0.3MnO3), where SrTiO3 is an insulator. At room temperature, i.e. in the semiconducting regime, it exhibits asymmetric current-voltage (I-V) characteristics akin to a p-n diode. The observed asymmetry in the I-V characteristics disappears at low temperatures where both the manganite layers are metallic. To the best of our knowledge, this is the first report of such a p-n diode, using the polaronic semiconducting regime of doped manganites.Comment: PostScript text and 2 figures, to be published in Appl. Phys. Lett

Magneto-transport properties of La₀.₇Ca₀.₃Mn0₃/SrTiO₃/La₀.₇Ce₀.₃MnO₃ tunnel junction

Hole-doped rare-earth manganite La0.7Ca0.3MnO3 and the electron-doped manganite La0.7Ce0.3MnO3 both show a metal-insulator transition around 250 K associated with a ferromagnetic transition and colossal magnetoresistance. In an earlier publication we have reported the rectifying characteristic of La0.7Ca0.3MnO3/SrTiO3/La0.7Ce0.3MnO3 tunnel junction at room temperature, showing that it is possible to fabricate a diode out of the polaronic insulator regime of doped manganites. Here we report the magneto-transport properties of such a tunnel junction above and below the metal-insulator transition. We show, from the large positive magnetoresistance of the tunnel junction at low temperature, that La0.7Ce0.3MnO3 could be a minority spin carrier ferromagnet. The implication of this observation is discussed

Magnetotransport properties of a room temperature rectifying tunnel junction made of electron and hole doped manganites

The hole-doped (p) manganite La0.7Ca0.3MnO3 and the electron-doped (n) manganite La0.7Ce0.3MnO3 undergo an insulator-to-metal transition at around 250 K, above which both behave as a polaronic semiconductor. We have fabricated an epitaxial trilayer (La0.7Ca0.3MnO3/SrTiO3/La0.7Ce0.3MnO3), where SrTiO3 is an insulator. At room temperature, i.e., in the semiconducting regime, it exhibits asymmetric current–voltage (I–V) characteristics akin to a p–n diode. The observed asymmetry in the I–V characteristics disappear at low temperatures where both the manganite layers are metallic. The I–V curves exhibit an intriguing temperature dependence in the presence of magnetic field. At room temperature, i.e., above the ordering temperature, we have a negative magnetoresistance (MR) and at low temperature we have a positive MR, indicative of a minority spin carrier band in La0.7Ce0.3MnO3. A possible mechanism for the observed effects are discussed