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

被引：64
作者：
Hejtmanek, J. [1 ]
Santava, E. [1 ]
Knizek, K. [1 ]
Marysko, M. [1 ]
Jirak, Z. [1 ]
Naito, T. [2 ]
Sasaki, H. [2 ]
Fujishiro, H. [2 ]
机构：
[1] ASCR, Inst Phys, Prague 16200 6, Czech Republic
[2] Iwate Univ, Fac Engn, Morioka, Iwate 0208551, Japan
来源：
PHYSICAL REVIEW B | 2010年 / 82卷 / 16期
关键词：
SPIN-STATE TRANSITION; MAGNETIC-PROPERTIES; CRYSTAL-FIELD; TRANSPORT; LA1-XSRXCOO3; PR; ND;
D O I：
10.1103/PhysRevB.82.165107
中图分类号：
T [工业技术];
学科分类号：
08 ;
摘要：
The magnetic, electric, and thermal properties of the (Ln(1-y)Y(y))(0.7)Ca0.3CoO3 perovskites (Ln=Pr, Nd) were investigated down to very low temperatures. The main attention was given to a peculiar metal- insulator (M-I) transition, which is observed in the praseodymium based samples with y=0.075 and 0.15 at TM-I=64 K and 132 K, respectively. The study suggests that the transition, reported originally in Pr0.5Ca0.5CoO3, is not due to a mere change in cobalt ions from the intermediate to the low- spin states but is associated also with a significant electron transfer between Pr3+ and Co3+/Co4+ sites, so that the praseodymium ions occur below TM-I in a mixed Pr3+/Pr4+ valence. The presence of Pr4+ ions in the insulating phase of the yttrium doped samples (Pr1-yYy)(0.7)Ca0.3CoO3 is evidenced by Schottky peak originating in Zeeman splitting of the ground-state Kramers doublet. The peak is absent in pure Pr0.7Ca0.3CoO3 in which metallic phase, based solely on nonKramers Pr3+ ions, is retained down to the lowest temperature.
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页数：7
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