## Resumen

We address the problem of the percolative phase separation in polycrystalline samples of Pr_{0.5-δ}Ca_{0.2+δ}Sr_{0.3} MnO_{3} for -0.04≤δ≤0.04 (hole doping n between 0.46 and 0.54). We perform measurements of x-ray diffraction, dc magnetization, electron spin resonance (ESR), and electrical resistivity. These samples show a paramagnetic (PM) to ferromagnetic (FM) transition at the Curie temperature T_{C}. However, for n>0.50 we found that in a wide temperature range below T_{C} an important PM volume still survives, coexisting with the FM phase. On lowering T below the charge-ordering (CO) temperature T_{CO} all the samples exhibit a coexistence of the FM metallic and CO (antiferromagnetic) phases. In the whole T range the FM phase fraction (X) decreases with increasing n. Furthermore, we show that only for n≤0.50 the metallic fraction is above the critical percolation threshold Xc≃15.5%. As a consequence, these samples show very different magnetoresistance properties. In addition, for n≤0.50 we observe a percolative metal-insulator transition at T_{MI}, and for T_{MI}<T<T_{CO} the insulating-like behavior generated by the enlargement of X with increasing T is well described by the percolation law p^{-1}=δ∼(X-X_{C})^{t}, where t is a critical exponent. On the basis of the values obtained for this exponent we discuss different possible percolation mechanisms, and suggest that a more deep understanding of geometric and dimensionality effects is needed in phase separated manganites. We present a complete T vs n phase diagram showing the magnetic and electric properties of the studied compound around half doping.

Idioma original | Inglés |
---|---|

Número de artículo | 134422 |

Páginas (desde-hasta) | 1344221-13442211 |

Número de páginas | 12097991 |

Publicación | Physical Review B - Condensed Matter and Materials Physics |

Volumen | 66 |

N.º | 13 |

Estado | Publicada - 1 oct. 2002 |

Publicado de forma externa | Sí |

## Huella

Profundice en los temas de investigación de 'Hole-doping dependence of percolative phase separation in Pr_{0.5-δ}Ca

_{0.2+δ}Sr

_{0.3}MnO

_{3}around half doping'. En conjunto forman una huella única.