Phase evolution of layered cobalt oxides versus varying corrugation of the cobalt-oxygen basal plane
Phase evolution of layered cobalt oxides versus varying corrugation of the cobalt-oxygen basal plane
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层状钴氧化物的相演化与钴氧基面不同波纹的关系
DOI：
10.1140/epjb/e2002-00407-3
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发表时间：
2002
期刊：
影响因子：
--
通讯作者：
Hua Wu
中科院分区：
文献类型：
--
作者：
Hua Wu
摘要：用密度泛函方法对一类新合成的层状钴氧化物(LCoS)提出了一般的自旋态模型和定性的物理图像。随着钴-氧层平面波纹的减小，LCoS从高自旋超交换耦合的反铁磁绝缘体演变为几乎-HS超交换耦合的反铁磁(FM)竞争系统，其中FM耦合是通过p-d交换调节的，主要具有平面O2p特征的离域PDσ空穴数量增加。初步认为，在波纹减弱的LCoS中，绝缘体-金属和/或AFM-FM转变可能需要大于0.3个/CoO_2基方的离域空穴。在LCoS中，可以通过改变钴-氧层两侧相邻层的离子尺寸来改变平面波纹(从而改变空穴浓度)来实现相位控制。此外，还提出了几个实验，以检验目前的模型和图像。
Abstract:A general spin-state model and a qualitative physical picture have been proposed for a class of lately synthesized layered cobalt oxides (LCOs) by means of density functional calculations. As the plane corrugation of the cobalt-oxygen layer decreases, the LCOs evolve from a high-spin (HS) superexchange-coupled antiferromagnetic (AFM) insulator to an almost-HS AFM/ferromagnetic (FM) competing system where the FM coupling is mediated via the p-d exchange by an increasing amount of delocalized pdσ holes having mainly the planar O 2p character. It is tentatively suggested that the delocalized holes more than 0.3 per CoO2 basal square are likely necessary for the insulator-metal and/or AFM-FM transitions in the corrugation-weakened LCOs. A phase control may be realized in LCOs by varying the plane corrugation (thus modifying the hole concentration) through an ionic-size change of the neighboring layers on both sides of the cobalt-oxygen layer. In addition, a few experiments are suggested for a check of the present model and picture.