钙钛矿型复合稀土铁氧化物电子结构的第一性原理研究

采用基于赝势平面波基组的第一性原理方法对一系列具有钙钛矿结构的复合稀土铁氧化物RFeO₃ (R＝镧系稀土元素)的构型和电子结构进行了系统研究. 考察了铁磁(FM)和反铁磁(AFM)两种磁结构, 其中AFM型在常温下更为稳定, 且其构型优化结果更接近于实验测量值. 不论是FM还是AFM构型, R原子的磁距均与自由R^3＋离子相同; 对于Fe原子, 在FM结构中的磁距较AFM类型来得小; 随着R原子序数的增加, 两种磁结构中Fe原子的磁距均呈减小趋势; 对于相同类型的RFeO₃化合物, 具有非常类似的能带结构, 其中AFM构型在费米能级处存在明显的带隙, 而FM型化合物则具有金属特性.

First Principles Study on the Electronic Properties of Rare-Earth Or-thoferrites with a Perovskite-Type Structure

Electronic properties of rare-earth orthoferrites,RFeO3 (R=rare earths) with optimized perovskite-type structures have been investigated systemically using the first principles method with a plane wave basis set. Ferromagnetic (FM) and antiferromagnetic (AFM) structures have been studied according to the different arrangements of magnetic moments of the Fe atoms. The results indicate that the AFM phase is more stable than the FM one at the normal temperature. The optimized structures of AFM phase are in good agreement with experiments. In both the FM and AFM phases,the magnetic moment of R atom is the same as that of the free R3 ion. For the Fe atom,the magnetic moment in the FM phase is smaller than in the AFM one,and it decreases for both structures with increasing atomic number of R atom. For a given phase,the band structures with different R atoms are very similar. The most distinct difference between the band structures of the FM and AFM phases is that,a band gap exists at the Fermi level for AFM arrangement but not for the FM phase.