Mössbauer Spectroscopy, as outlined in Chapter 2, is an effective probe of magnetic ordering in materials. In particular it can distinguish different contributions to magnetic structure arising from different ions and different sites as in the Fe and Fe ions on A and B sites in FeO (see Chapter 8). It cannot, however, provide a complete description of the magnetism alone. For example, Mössbauer Spectroscopy in zero applied field cannot distinguish between ferromagnetic and antiferromagnetic ordering. It is sensitive only to the particular Mössbauer isotope being probed and the spectra take a relatively long time to accumulate. Magnetometry can produce results on the total moment of the system and its variation with applied field and temperature relatively quickly and easily, providing complementary data to the Mössbauer spectrum as well as other techniques.