Metal-insulator transition and the Pr$^{3+}$/Pr$^{4+}$ valence shift in (Pr$_{1-y}$Y$_{y}$)$_{0.7}$Ca$_{0.3}$CoO$_3$

J. Hejtmánek; E. Šantavá; K. Knížek; M. Maryško; Z. Jirák T. Naito; H. Sasaki; H. Fujishiro

doi:10.1103/PhysRevB.82.165107

paper

Metal-insulator transition and the Pr $^{3 +}$ /Pr $^{4 +}$ valence shift in (Pr $_{1 - y}$ Y $_{y}$ ) $_{0.7}$ Ca $_{0.3}$ CoO $_{3}$

arXiv:1004.4100 · doi:10.1103/PhysRevB.82.165107

Abstract

The magnetic, electric and thermal properties of the ( $L n_{1 - y}$ Y $_{y}$ ) $_{0.7}$ Ca $_{0.3}$ CoO $_{3}$ perovskites ( $L n$ ~=~Pr, Nd) were investigated down to very low temperatures. The main attention was given to a peculiar metal-insulator transition, which is observed in the praseodymium based samples with $y = 0.075$ and 0.15 at $T_{M - I} = 64$ and 132~K, respectively. The study suggests that the transition, reported originally in Pr $_{0.5}$ Ca $_{0.5}$ CoO $_{3}$ , is not due to a mere change of cobalt ions from the intermediate- to the low-spin states, but is associated also with a significant electron transfer between Pr $^{3 +}$ and Co $^{3 +}$ /Co $^{4 +}$ sites, so that the praseodymium ions occur below $T_{M - I}$ in a mixed Pr $^{3 +}$ /Pr $^{4 +}$ valence. The presence of Pr $^{4 +}$ ions in the insulating phase of the yttrium doped samples (Pr $_{1 - y}$ Y $_{y}$ ) $_{0.7}$ Ca $_{0.3}$ CoO $_{3}$ is evidenced by Schottky peak originating in Zeeman splitting of the ground state Kramers doublet. The peak is absent in pure Pr $_{0.7}$ Ca $_{0.3}$ CoO $_{3}$ in which metallic phase, based solely on non-Kramers Pr $^{3 +}$ ions, is retained down to the lowest temperature.

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Metal-insulator transition and the Pr $^{3 +}$ /Pr $^{4 +}$ valence shift in (Pr $_{1 - y}$ Y $_{y}$ ) $_{0.7}$ Ca $_{0.3}$ CoO $_{3}$

Abstract

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Metal-insulator transition and the Pr3+/Pr4+ valence shift in (Pr1−y​Yy​)0.7​Ca0.3​CoO3​

Abstract

References in corpus (4)

Cited by in corpus (26)

Metal-insulator transition and the Pr $^{3 +}$ /Pr $^{4 +}$ valence shift in (Pr $_{1 - y}$ Y $_{y}$ ) $_{0.7}$ Ca $_{0.3}$ CoO $_{3}$