Study of phase separation through the charge order to ferromagnetic crossover in (La yPr 1−y) 0.5Ca 0.5MnO 3

Abstract

We present a magnetic phase diagram for the (La y Pr 1− y ) 0,5Ca 0,5MnO 3 family with different degrees of La–Pr substitution ( y) based on electric resistivity, magnetization, X-ray diffraction at different temperatures and thermal expansion experiments. In this series, the structural distortion due to the variation of the mean ionic radius of site A ( r A), by decreasing y, induces a rapid diminution of the ferromagnetic (FM) Curie temperature ( T C) and an increase of the charge-order (CO) temperature ( T CO). The crossover between T C and T CO determines a critical tolerance factor ( t c≅0.975), which is consistent with previous reports on other manganites with the same Mn 3+/Mn 4+ ratio. For tolerance factors close to t c, we observe the coexistence of different amounts of FM and CO phases depending on y. The disorder introduced by y and the presence of phase separation around t c induces a smooth and continuous variation of the structural, electrical and magnetic properties when crossing through t c.