Mouml;ssbauer effect of57Fe has been used to study the magnetic properties of Fe3plus;ions in frozen ferric perchlorate aqueous solutions. The Mouml;ssbauer data for solutions withpH higher than about 2.5 can be understood by a model in which Fe3plus;ions form antiferromagnetic fine particles that show superparamagnetism above the blocking temperature. In applied magnetic fields, unambiguous ``anisotropic spin relaxation'' spectra in the superparamagnetic state are observed. The decrease in susceptibility at room temperature may be also explained by this model. The solutions with lowpH show paramagnetic spectra even at low temperatures.
展开▼
