LATTICE-DYNAMICS OF LA2NIO4
LATTICE-DYNAMICS OF LA2NIO4
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DOI：
10.1103/physrevb.40.2229
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发表时间：
1989-08-01
影响因子：
3.7
通讯作者：
GOMPF, F
中科院分区：
文献类型：
--
作者：
PINTSCHOVIUS, L;BASSAT, JM;GOMPF, F
采用非弹性中子散射法研究了与la2cuo4同构的la2nio4的晶格动力学。在主要对称方向上确定了所有声子分支[100]、[110]和[001]。此外，在多晶样品上直接测量声子态密度。基于具有库仑力各向异性筛选的刚性离子模型对结果进行了分析，以考虑电子性质的二维特征。发现库仑力降低了X点处软模态的频率。该模态与la2cuo4中的软模态具有相同的特征向量，即它是八面体围绕[110]轴的倾斜模态。Ni原子的负平面呼吸变形性对于再现涉及平面内Ni- o拉伸振动的分支中的明显异常是必要的。与红外数据的比较得出了基底平面内偏振模式的非常好的一致性，而沿c轴偏振模式的严重分歧被发现。与la2cuo4的数据比较表明，la2nio4和la2cuo4的晶格动力学没有太大的不同。
The lattice dynamics of La 2 NiO 4, which is isostructural to La 2 CuO 4, was investigated by inelastic neutron scattering. All phonon branches were determined in the main symmetry directions [100],[110], and [001]. In addition, the phonon density of states was measured directly on a polycrystalline sample. The results are analyzed on the basis of a rigid-ion model with anisotropic screening of the Coulomb forces to account for the two-dimensional character of the electronic properties. The Coulomb forces were found to lower the frequency of the soft mode at the X point. This mode has the same eigenvector as the soft mode in La 2 CuO 4, ie, it is a tilt mode of the octahedra around a [110] axis. A negative planar breathing deformability of the Ni atom was necessary to reproduce the pronounced anomalies in the branches involving in-plane Ni-O stretching vibrations. A comparison to infrared data yielded very good agreement for modes polarized within the basal plane, whereas a serious disagreement was found for modes polarized along the c axis. A comparison with the data of La 2 CuO 4 shows that the lattice dynamics of La 2 NiO 4 and La 2 CuO 4 are not very different.