Magnetic and structural study of La1.8Sr0.2NiO4.
Magnetic and structural study of La1.8Sr0.2NiO4.
复制标题
La1.8Sr0.2NiO4的磁性和结构研究。
DOI：
10.1103/physrevb.43.448
复制
发表时间：
1991
期刊：
影响因子：
--
通讯作者：
Honig
中科院分区：
文献类型：
--
作者：
Lander;Brown;Stassis;Gopalan;Spalek;Honig
对（La{sub 1.8}Sr{sub 0.2}）NiO{sub 4}单晶进行了极化中子和非极化中子的中子衍射实验。材料在室温下为四边形（{ital I}4/{ital mmm}），但在120{正负}5k时发生二级相变，扭曲为正交（{ital Bmab}）改性。结构参数与纯La{sub 2}NiO{sub 4}相似。磁化率在低温下具有高度的各向异性，{chi}{sub {ital a}{ital b}}（垂直于长轴施加的场）在{类似于}17 K处出现峰值。然而，我们没有发现长程磁序存在的证据。我们推测低温态为各向异性自旋玻璃，冻结温度为17k。用偏振中子衍射测量了在4.6 T、20 K场强下的感应磁化密度。结果可以通过使用稍微扩展的Ni{sup 2+}形状因子和在La位点调用小的正磁化率来理解。也有证据表明Ni和O(2)原子沿{粗体c}轴是共价的。令人惊讶的是，在{ital ab}平面上没有发现异常的效应，我们可以预期在Ni {ital d}{次{ital x}}{supmore»2}{-}{ital y}{sup 2}和O {ital p}{次{ital x}}，{p}{次{ital y}}轨道之间有很强的共价关系。这些中子实验所得的总矩与磁化实验所得的总矩符合得很好。«少
Neutron-diffraction experiments with both polarized and unpolarized neutrons have been performed on single crystals of (La{sub 1.8}Sr{sub 0.2})NiO{sub 4}. The material is tetragonal at room temperature ({ital I}4/{ital mmm}) but distorts to the orthorhombic ({ital Bmab}) modification at 120{plus minus}5 K with a second-order phase transition. The structural parameters are similar to those in the pure La{sub 2}NiO{sub 4}. The susceptibility is highly anisotropic at low temperature, with {chi}{sub {ital a}{ital b}} (field applied perpendicular to the long axis) showing a peak at {similar to}17 K. However, we have found no evidence for long-range magnetic order. We speculate that the low-temperature state is an anisotropic spin glass, with 17 K being the freezing temperature. Polarized-neutron diffraction has been used to measure the induced magnetization density in a field of 4.6 T and at 20 K. The results can be understood by using a slightly expanded Ni{sup 2+} form factor and invoking a small positive susceptibility at the La site. There is also evidence for covalency between the Ni and O(2) atoms along the {bold c} axis. Surprisingly, no unusual effects are found in the {ital ab} plane where we might expect strong covalency between the Ni {ital d}{sub {ital x}}{supmore » 2}{minus}{ital y}{sup 2} and O {ital p}{sub {ital x}},{ital p}{sub {ital y}} orbitals. The total moment as determined by these neutron experiments is in good agreement with that determined by magnetization experiments.« less