Materials Science and Engineering Program/Mechanical Engineering, University of Texas at Austin, Austin, Texas 78712, USA.
Phys Rev Lett. 2012 Jun 8;108(23):236403. doi: 10.1103/PhysRevLett.108.236403.
We report a comprehensive high-pressure study on the triple-layer T'-La4Ni3O8 with a suite of experimental probes, including structure determination, magnetic, and transport properties up to 50 GPa. Consistent with a recent ab inito calculation, application of hydrostatic pressure suppresses an insulator-metal spin-state transition at P(c)≈6 GPa. However, a low-spin metallic phase does not emerge after the high-spin state is suppressed to the lowest temperature. For P>20 GPa, the ambient T' structure transforms gradually to a T(†)-type structure, which involves a structural reconstruction from fluorite La-O2-La blocks under low pressures to rock-salt LaO-LaO blocks under high pressures. Absence of the metallic phase under pressure has been discussed in terms of local displacements of O2- ions in the fluorite block under pressure before a global T(†) phase is established.
我们报告了对具有一系列实验探针的三层 T'-La4Ni3O8 的综合高压研究，包括结构确定、磁性和输运性质，最高可达 50 GPa。与最近的从头算计算一致，静水压力抑制了在 P(c)≈6 GPa 处的绝缘-金属自旋态转变。然而，在抑制到最低温度后，高自旋态不会出现低自旋金属相。对于 P>20 GPa，环境 T'结构逐渐转变为 T(†)-型结构，这涉及在低压力下从萤石 La-O2-La 块到高压力下的岩盐 LaO-LaO 块的结构重构。在建立全局 T(†)相之前，在压力下萤石块中 O2-离子的局部位移导致压力下不存在金属相。
