高压四重钙钛矿CeCuMnO中的电荷与轨道有序以及结构不稳定性

Charge and orbital orders and structural instability in high-pressure quadruple perovskite CeCuMnO.

作者信息

Zhang Lei, Matsushita Yoshitaka, Katsuya Yoshio, Tanaka Masahiko, Yamaura Kazunari, Belik Alexei A

机构信息

Research Center for Functional Materials, National Institute for Materials Science (NIMS), Namiki 1-1, Tsukuba, Ibaraki 305-0044, Japan. Graduate School of Chemical Sciences and Engineering, Hokkaido University, North 10 West 8, Kita-ku, Sapporo, Hokkaido 060-0810, Japan.

出版信息

J Phys Condens Matter. 2018 Feb 21;30(7):074003. doi: 10.1088/1361-648X/aaa5e4.

DOI:10.1088/1361-648X/aaa5e4

PMID:29359703

Abstract

We prepared a quadruple perovskite CeCuMnO under high-pressure and high-temperature conditions at 6 GPa and about 1670 K and investigated its structural, magnetic and transport properties. CeCuMnO crystallizes in space group Im-3 above T = 297 K; below this temperature, it adopts space group R-3 with the 1:3 (Mn:Mn) charge and orbital orders. Unusual compressed MnO octahedra are realized in CeCuMnO similar to CaMnO with the -Q Jahn-Teller distortion mode. Below about 90 K, structural instability takes place with phase separation and the appearance of competing phases; and below 70 K, two R-3 phases coexist. CeCuMnO exhibits a ferromagnetic-like transition below T = 140 K, and it is a semiconductor with the magnetoresistance reaching about -40% at 140 K and 70 kOe. We argued that the valence of Ce is +3 in CeCuMnO with the Ce([Formula: see text])([Formula: see text])O charge distribution in the charge-ordered R-3 phase and Ce([Formula: see text])([Formula: see text])O in the charge-disordered Im-3 phase.

摘要

我们在6吉帕斯卡和约1670开尔文的高压和高温条件下制备了一种四重钙钛矿CeCuMnO，并研究了其结构、磁性和输运性质。CeCuMnO在T = 297开尔文以上结晶于空间群Im-3；低于此温度时，它采用具有1:3（Mn:Mn）电荷和轨道有序的空间群R-3。在CeCuMnO中实现了不寻常的压缩MnO八面体，类似于具有-Q Jahn-Teller畸变模式的CaMnO。在约90开尔文以下，发生结构不稳定性，伴有相分离和竞争相的出现；在70开尔文以下，两个R-3相共存。CeCuMnO在T = 140开尔文以下表现出类似铁磁的转变，并且它是一种半导体，在140开尔文和70千奥斯特时磁电阻达到约-40%。我们认为，在电荷有序的R-3相中，CeCuMnO中Ce的化合价为+3，电荷分布为Ce([公式：见原文])([公式：见原文])O，在电荷无序的Im-3相中为Ce([公式：见原文])([公式：见原文])O。