论文标题
Laalo3晶体中CE3+活化剂离子的掺入：EPR和NMR研究
Incorporation of the Ce3+ activator ions in LaAlO3 crystals: EPR and NMR study
论文作者
论文摘要
这项工作报告了通过微脱落方法生长的LAALO3单晶中CE3+掺入的EPR和NMR研究的结果，CE浓度的范围从x = 0.1 at。at。％至100 at。％at。％。从EPR测量值，CE3+ G张量参数是CE浓度的函数。 G量张量即使在三角相（x <10 at。％）也具有正栓对称性，这表明在该离子附近，在La位置降低了CE降低晶格对称性。通过27AL和139LA高分辨率NMR测量值进一步研究了LA1-XCEXALO3晶体的局部性质。发现139LA化学位移具有费米接触相互作用。随着CE浓度，它在x = 0.5时线性增加165 ppm。由于这种强烈的费米接触相互作用，在139LA NMR光谱中解析了与不同CE-O-LA自旋传输通道相对应的分离峰。另一方面，在27AL NMR光谱中没有可见的费米接触相互作用。但是，这些光谱包含卫星峰，该卫星峰值随着CE浓度的增加而保持该峰的位置不变。这被解释为与EPR数据一致的CE离子附近晶体结构修饰的表现。因此，Laalo3中Ce3+的光学性质将是由该离子附近的局部晶体结构确定的。
This work reports the results of EPR and NMR study of the Ce3+ incorporation in LaAlO3 single crystals grown by the micro-pulling-down method in the range of the Ce concentrations from x=0.1 at.% up to 100 at.%. From EPR measurements, Ce3+ g tensor parameters were obtained as function of Ce concentration. The g tensor has orthorhombic symmetry even in the trigonal phase (x < 10 at.%) suggesting that the incorporation of Ce at La site lowers lattice symmetry near this ion. The local properties of the La1-xCexAlO3 crystals were further studied by 27Al and 139La high-resolution NMR measurements. It was found that 139La chemical shift has the Fermi contact interaction origin. It linearly increases with Ce concentration up to 165 ppm at x = 0.5. Due to this strong Fermi contact interaction, separated peaks corresponding to different Ce-O-La spin transfer passways are resolved in the 139La NMR spectra. On the other hand, no Fermi contact interaction is visible in 27Al NMR spectra. However, these spectra contain satellite peak which intensity linearly increases with increase of Ce concentration leaving position of this peak unchanged. This was interpreted as manifestation of crystal structure modification in vicinity of Ce ions in agreement with EPR data. Thus, optical properties of Ce3+ in LaAlO3 will be namely determined by the local crystal structure near this ion.
