Magnetic Ions in Crystals
Stevens, K. W.
There have been many demonstrations, particularly for magnetic impurity ions in crystals, that spin-Hamiltonians are able to account for a wide range of experimental results in terms of much smaller numbers of parameters. Yet they were originally derived from crystal field theory, which contains a logical flaw, electrons on the magnetic ions are distinguished from those on the ligands. Thus there is a challenge: to replace crystal field theory...