The first part of this lecture starts with an introduction about a hyperfine field. It will deal with all properties of this very informative physical quantity. So the basic mechanisms and origins of the hyperfine field, its vector nature, the correspondence to the magnetic moment of the atom electronic shell and its dynamic aspects will be treated. As a method for measurement of hyperfine fields the Mössbauer spectrometry will be used. We will not consider other techniques as NMR or PAC. We focus on the special properties of ⁵⁷Fe the 'natural' isotope for steels.
In the second part two examples will be presented. We deal with exotic magnetic properties on 'nonmagnetic steels' exhibiting transitions from a ferromagnet to a spin glass at low temperatures. We demonstrate that hyperfine fields are very valuable 'finger prints' for characterizing different phases in a complex alloy. As example nanocrystallites are considered produced during the crystalization of an amorphous alloy.
The tendency of the lecture is to demonstrate that it is very fruitful to combine 'classical' global methods with modern local nuclear experimental techniques of investigations. Additionally to Mössbauer spectrometry investigations we apply measurements of magnetization, of electrical resistivity, X-Ray diffraction or electron microscopy in order to elucidate the atomistic reasons for properties and technology of new materials in question.