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Which materials can be studied with electron-spin resonance?
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magnetic resonance
Figure 1: Precession of a magnetic dipole moment μ in the presence of a constant field H and a rotating field H′ (see text)
Electron-spin resonance (ESR), also known as electron paramagnetic resonance, is observed in a restricted class of substances that possess unpaired electrons. Materials that can be studied using this technique include:12
- Transition elements: Elements characterized by unfilled inner electronic shells, including the iron, lanthanoid (rare earth), palladium, platinum, and actinoid groups.1
- Free radicals: Molecular fragments that are ideally suited for ESR study, whether in concentrated form or dilute solutions.1
- Metals: Specifically for studying the behavior of free or conduction electrons.12
- Paramagnetic defects and impurity centers: This includes imperfections such as vacancies at lattice sites and impurity centers in crystals. A notable example is the study of phosphorus, arsenic, and antimony impurities substituted in semiconductors like silicon and germanium.1
- Metastable states: Excited states in molecular crystals that are long-lived because energy transfer via radiation does not occur.2
The technique is highly sensitive to the environment, as the unfilled subshells of atoms are easily distorted by interactions within bulk matter.1