Study on the stability of charge-ordered state and rectifying properties of heteroepitaxial structure for manganites

Abstract

We report the study on the stability of charge-ordered (CO) state and rectifying properties of heteroepitaxial structure for manganites R(1-x)Ca(x)MnO(3) (R = La, Pr, and Sm) by measuring magnetoresistance, magnetization, specific heat, 1-v characteristics, and X-ray diffraction. For the La(1-x)Ca(x)MnO(3) system, near the Ca(2+) concentration of x=0.75 the CO state is mostly stabilized and insensitive to external magnetic fields, which is supported by the charge transport, magnetic, and specific heat properties. By analyzing powder X-ray diffraction patterns, we found that the Jahn-Teller (JT) distortion in the CO state is the largest at x=0.75, which confirms the close relationship between the JT lattice distortion and the stability of the CO state for La(1-x)Ca(x)MnO(3). The stability of the CO state is also related to the A-site average ionic radius, . With decreasing the radius of the doped rare-earth elements (La, Pr, and Sm), the most stable CO state for the each doped system shifts gradually toward lower Ca(2+) concentration. In addition, we have fabricated simple p-n junctions using a heteroepitaxial structure of La(1-x)Ca(x)MnO(3)/Nb-doped SrTiO(3). These junctions show good rectifying properties for temperature from 85 to 305 K. The photovoltage as a function of light wavelength at room temperature has also been studied and the maximum photovoltage can reach 180 mV. The good rectifying behaviors and strong photovoltaic effect make these simple p-n junctions promising for applications.