Electron Spin Resonance

Electron Spin Resonance

Electron Spin Resonance (ESR) is a phenomenon usefull for the investigation of materials which contain unpaired spins. Those are caused by various sources. One are not completely filled atomic shells, however, the more interesting ESR signals arise from different circumstances combined in the term defect. For instance, a important one is impurities of semiconductors or isolators which can trap electron or holes. Therefore this measuring technique is very powerfull evaluation of material properties and is used in lots of research fields in physics, chemistry and biology.

Physical background

As the term Electron Spin Resonance already implies, the most essential part of the entire topic is the Spin, an intrinsic angular momentum of the electron. In an atom most of the electron are paired regarding spin. That is, each electron has a partner with an opposite spin, creating a zero net spin. Depending on the electron configuration of an atom or one step above in molecules/solids, it is possible that there are a few or even many single electrons, being up to material.