Mössbauer effect in small particles

Mössbauer spectroscopy is very sensitive to the special magnetic properties of ultrafine particles. Studies of particles in the superparamagnetic state allow determination of the particle size and the magnetic anisotropy energy constant A strong magnetic interaction between the particles may result in ordering of the magnetic moments of particles which would be superparamagnetic if they were non-interacting. This so-called superferromagnetic state can also be characterized by Mössbauer spectroscopy measurements. Furthermore, because a large fraction of the atoms in very small particles are in the surface layer, Mössbauer spectroscopy can be applied for studies of surface magnetism in small particles.