Liu M F, Du Z Z, Xie Y L, Li X, Yan Z B, Liu J-M
Laboratory of Solid State Microstructures and Innovative Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China.
1] Laboratory of Solid State Microstructures and Innovative Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China [2] Institute for Advanced Materials and Laboratory of Quantum Engineering and Materials, South China Normal University, Guangzhou 510006, China.
Sci Rep. 2015 Apr 24;5:9922. doi: 10.1038/srep09922.
The eg-orbital double-exchange mechanism as the core of physics of colossal magnetoresistance (CMR) manganites is well known, which usually covers up the role of super-exchange at the t2g-orbitals. The role of the double-exchange mechanism is maximized in La0.7Ca0.3MnO3, leading to the concurrent metal-insulator transition and ferromagnetic transition as well as CMR effect. In this work, by a set of synchronous Ru-substitution and Ca-substitution experiments on La0.7-yCa0.3+yMn1-yRuyO3, we demonstrate that the optimal ferromagnetism in La0.7Ca0.3MnO3 can be further enhanced. It is also found that the metal-insulator transition and magnetic transition can be separately modulated. By well-designed experimental schemes with which the Mn(3+)-Mn(4+) double-exchange is damaged as weakly as possible, it is revealed that this ferromagnetism enhancement is attributed to the Mn-Ru t2g ferromagnetic super-exchange. The present work allows a platform on which the electro-transport and magnetism of rare-earth manganites can be controlled by means of the t2g-orbital physics of strongly correlated transition metal oxides.
作为巨磁电阻（CMR）锰氧化物物理学核心的eg轨道双交换机制广为人知，它通常掩盖了t2g轨道上超交换的作用。双交换机制的作用在La0.7Ca0.3MnO3中达到最大化，导致同时发生金属-绝缘体转变和铁磁转变以及CMR效应。在这项工作中，通过对La0.7-yCa0.3+yMn1-yRuyO3进行一组同步的Ru替代和Ca替代实验，我们证明La0.7Ca0.3MnO3中的最佳铁磁性可以进一步增强。还发现金属-绝缘体转变和磁转变可以分别被调制。通过精心设计的实验方案，尽可能微弱地破坏Mn(3+)-Mn(4+)双交换，结果表明这种铁磁性增强归因于Mn-Ru t2g铁磁超交换。目前的工作提供了一个平台，在这个平台上，稀土锰氧化物的电输运和磁性可以通过强关联过渡金属氧化物的t2g轨道物理学来控制。
