Paramagnetic Resonance in Salts of the Iron Group - A Preliminary Survey: II. Experimental Results

Over a hundred salts of the iron group have been examined by the method of paramagnetic resonance at a wavelength of 3 cm., using magnetic fields up to 15 kilogauss at room temperature. The cases in which no absorption is observed have been further investigated at lower temperatures and shorter wavelengths. The results are considered for each paramagnetic ion in relation to the effects of the crystalline field theory. The ions Ti +++ , Fe ++ and Co ++ are found to have abnormally small spin-lattice relaxation times, while in Fe ++ and Ni ++ the energy levels are separated in zero magnetic field by as much as 1 cm -1 in most salts. A preliminary investigation of salts of the rare earth group indicates that spin-lattice relaxation times for most of these ions are also very short at temperatures above those of liquid hydrogen.