Ferromagnetic polarons in La0.5Ca0.5MnO3 and La0.33Ca0.67MnO3
Ferromagnetic polarons in La0.5Ca0.5MnO3 and La0.33Ca0.67MnO3
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DOI：
10.1103/physrevb.67.220404
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发表时间：
2003-02
影响因子：
3.7
通讯作者：
G. Zheng;C. H. Patterson
中科院分区：
文献类型：
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作者：
G. Zheng;C. H. Patterson
对全磁性晶胞中的 La 1 - x Ca x MnO 3 (x=0.5 和 x=0.67) 进行的无限制 Hartree-Fock 计算表明，这些化合物的磁性基态由“铁磁分子”或以人字形排列的极化子组成。每个极化子由两个或三个由 O - 离子分隔的 Mn 离子组成，其磁矩与 Mn 离子的磁矩相反。极化子内的铁磁耦合较强，而极化子之间的耦合相对较弱。 x=0.5 化合物中 Mn 离子的磁矩范围为 3.8μ b 至 3.9 μ B ，O - 离子的磁矩为 -0.7μ B 。每个极化子的净磁矩为 7.0μ B ，与最近报道的电子显微镜磁化测量结果非常吻合。这里报道的电子结构的极化子性质显然与最近为Pr 0 提出的齐纳极化子模型有关。 6 0 铜 0 。 4 0 MnO 3 基于中子散射数据。
Unrestricted Hartree-Fock calculations on La 1 - x Ca x MnO 3 (x=0.5 and x=0.67) in the full magnetic unit cell show that the magnetic ground states of these compounds consist of "ferromagnetic molecules" or polarons ordered in herring-bone patterns. Each polaron consists of either two or three Mn ions separated by O - ions with a magnetic moment opposite to those of the Mn ions. Ferromagnetic coupling within the polarons is strong, while coupling between them is relatively weak. Magnetic moments on the Mn ions range between 3.8μ b and 3.9 μ B in the x=0.5 compound and moments on the O - ions are -0.7μ B . Each polaron has a net magnetic moment of 7.0μ B , in a good agreement with recently reported magnetization measurements from electron microscopy. The polaronic nature of the electronic structure reported here is obviously related to the Zener polaron model recently proposed for Pr 0 . 6 0 Cu 0 . 4 0 MnO 3 on the basis of neutron-scattering data.