Magnetic relaxation effects in frozen ferric perchlorate solutions observed by the Mossbauer effect

The Mossbauer spectra were measured in frozen ferric perchlorate solution of different PH. at temperatures from 2.8 to 77 degrees K. The internal magnetic field, as evaluated from the spectra, was found to be dependent on PH. The hyperfine magnetic structure of the spectra can be attributed at lower pH values to paramagnetic relaxation effect and at higher pH values to magnetic dipole-dipole interaction between the high spin ferric ions.