DOUBLE EXCHANGE VIA DEGENERATE ORBITALS
DOUBLE EXCHANGE VIA DEGENERATE ORBITALS
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通过简并轨道的双重交换
DOI：
10.1103/physrevlett.82.1016
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发表时间：
1998
影响因子：
8.6
通讯作者：
D. Khomskii
中科院分区：
文献类型：
--
作者：
J. Brink;D. Khomskii
我们考虑双交换系统中，掺杂的电子占据简并轨道，治疗的实际情况与双简并EG轨道。我们表明，轨道简并导致一般各向异性磁结构的形成，特别是，取决于掺杂浓度，层状的A型和链状结构的C型的磁结构是稳定的。我们得到的相图提供了一个解释实验观察到的磁性结构的一些过掺杂（电子掺杂）锰氧化物的类型Nd 12 xSrxMnO 3，Pr 1 2 xSrxMnO 3，和Sm 12 xCaxMnO 3，与x。0.5. [S 0031 -9007（98）08277-5] PACS编号：75.30.Et，75.30.Vn双交换（DE）模型[1 - 3]是金属体系铁磁性的主要模型之一。最近，随着对具有巨磁电阻（CMR）的锰氧化物的积极研究，对该模型的兴趣重新燃起[4]。虽然目前还不清楚DE是否可以单独解释锰氧化物中的CMR [5]，并且模型本身也存在一些问题（例如，相分离的趋势[6 - 9]），双交换机制是理论上理解CMR效应的必要成分[5，10]，并且仍然是至少对La 12 xMxMnO 3（M › Ca，Sr）型掺杂锰氧化物中铁磁态存在的主要解释。在CMR材料的研究中，大多数实验数据是针对空穴掺杂的锰氧化物（x，0.5）获得的，因为通常在该掺杂范围内观察到CMR。然而，最近，有趣的数据出现在过掺杂（或电子掺杂）锰氧化物的性质（x。0.5）。理论上，在传统的DE模型中，人们期望对于小x和对于x，1，定性地类似的行为。然而，在实验上，存在非常强的不对称性。研究了掺杂锰氧化物对x，0.5和x。0.5是完全不同的特别地，对于x，观察到非常稳定的绝缘条纹相。0.5用掺杂确定的周期[11]，
We consider the double exchange for systems in which doped electrons occupy degenerate orbitals, treating the realistic situation with double degenerate eg orbitals. We show that the orbital degeneracy leads in general to the formation of anisotropic magnetic structures and that, in particular, depending on the doping concentration, the layered magnetic structures of the A-type and the chainlike structures of the C-type are stabilized. The phase diagram that we obtain provides an explanation for the experimentally observed magnetic structures of some overdoped (electron-doped) manganites of the type Nd12xSrxMnO3 ,P r 1 2 xSrxMnO3, and Sm12xCaxMnO3, with x . 0.5. [S0031-9007(98)08277-5] PACS numbers: 75.30.Et, 75.30.Vn The double-exchange (DE) model [1 ‐ 3] is one of the main models of ferromagnetism in metallic systems. The interest in this model was renewed recently in connection with the active study of the manganites with colossal magnetoresistance (CMR) [4]. Although it is not yet clear whether DE alone can explain the CMR in manganites [5], and there are some problems with the model itself (e.g., the tendency to phase separation [6 ‐ 9]), the double-exchange mechanism is a necessary ingredient for the theoretical understanding of the CMR effect [5,10] and remains the main explanation at least of the presence of the ferromagnetic state in doped manganites of the type La12xMxMnO3 (M › Ca, Sr). Most experimental data in the study of the CMR materials are obtained for the hole-doped manganites (x , 0.5) as it is usually in this doping range that CMR is observed. Recently, however, interesting data appeared on the properties of overdoped (or electron-doped) manganites (x . 0.5). Theoretically, in a conventional DE model one expects qualitatively similar behavior for small x and for x , 1. Experimentally, however, there exists a very strong asymmetry. The behavior of doped manganites for x , 0.5 and x . 0.5 is drastically different. In particular, a very stable insulating stripe phase is observed for x . 0.5 with the period determined by doping [11],