Application of perturbed angular correlations to oxides

✍ Scribed by Michael Uhrmacher

• Book ID: 103886733
• Publisher: Elsevier Science
• Year: 2007
• Tongue: English
• Weight: 561 KB
• Volume: 389
• Category: Article
• ISSN: 0921-4526
• DOI: 10.1016/j.physb.2006.07.025

✦ Synopsis

Nearly all elements can be oxidized and develop oxides, often with different oxygen contents and in different crystalline phases. Applying the classical perturbed angular correlation (PAC)-probes 111 In/ 111 Cd or 181 Hf/ 181 Ta, the probes are usually found on unperturbed cation lattice sites surrounded by oxygen atoms. Using different oxides of the same structure or comparing different crystal classes the position of the oxygen neighbours near the probe can be varied in a wide range. This allows testing theoretical concepts of electric field gradient (EFG) calculation.

In general, the melting point of an oxide is very high, and the PAC experiments span a huge temperature range from T m ¼ 10 to 1700 K. Two temperature regions are known, where 111 In/ 111 Cd probes show dynamic hyperfine-interactions, which occur when the EFG changes direction or strength during the lifetime of the probe. At low temperatures the electron capture ''after-effect'' is observed, caused by a low availability of charge carriers in semiconducting or isolating oxides. At very high temperatures intrinsic defects or mobile atoms in ternary oxides move so fast, that undamped perturbation functions arise.

Realizing the big impact of STM and AFM to the surface science, a probing technique like PAC for the next neighbours inside a sample seems to be attractive. In the past, numerous discussions asked whether the inserted PAC-probes are really spies-only observers-or if they actually change that neighbourhood, that they are supposed to analyse. Distortions in oxides are discussed.