Oxygen isotope effect and phase separation in the optical conductivity of (La$_{0.5}$Pr$_{0.5}$)$_{0.7}$Ca$_{0.3}$MnO$_3$ thin films

F. P. Mena; A. B. Kuzmenko; A. Hadipour; J. L. M. van Mechelen; D. van der Marel; N. A. Babushkina

doi:10.1103/PhysRevB.72.134422

paper

Oxygen isotope effect and phase separation in the optical conductivity of (La $_{0.5}$ Pr $_{0.5}$ ) $_{0.7}$ Ca $_{0.3}$ MnO $_{3}$ thin films

arXiv:cond-mat/0510337 · doi:10.1103/PhysRevB.72.134422

Abstract

The optical conductivities of films of (La $_{0.5}$ Pr $_{0.5}$ ) $_{0.7}$ Ca $_{0.3}$ MnO $_{3}$ with different oxygen isotopes ( $^{16}$ O and $^{18}$ O) have been determined in the spectral range from 0.3 to 4.3 eV using a combination of transmission in the mid-infrared and ellipsometry from the near-infrared to ultra-violet regions. We have found that the isotope exchange strongly affects the optical response in the ferromagnetic phase in a broad frequency range, in contrast to the almost isotope-independent optical conductivity above $T_{C}$ . The substitution by $^{18}$ O strongly suppresses the Drude response and a mid-infrared peak while enhancing the conductivity peak at 1.5 eV. A qualitative explanation can be given in terms of the phase separation present in these materials. Moreover, the optical response is similar to the one extracted from measurements in polished samples and other thin films, which signals to the importance of internal strain.

arXiv comment11 pages, 11 figures, to appear in PRB

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Oxygen isotope effect and phase separation in the optical conductivity of (La0.5​Pr0.5​)0.7​Ca0.3​MnO3​ thin films

Abstract

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Oxygen isotope effect and phase separation in the optical conductivity of (La $_{0.5}$ Pr $_{0.5}$ ) $_{0.7}$ Ca $_{0.3}$ MnO $_{3}$ thin films