Abstract:
From the time Van Vleck: Theory of Electric and Magnetic Susceptibilities put forward his theory of atomic magnetism the apparently anomalous behaviour of the Group VIII transition metals, particularly the Platinum and Palladium triads, has caused considerable interest and there have been a number of theories put forward. Until recently little experimental evidence has been available.
When it was shown that the Van Vleck theory, which accounted quite well for the Rare Earths, did not do so for the Transition metals, Bose and Stoner advanced their 'spin only' theory. This was based on the theory that the orbital contribution, which accounted for the moments of the Rare Earths, was in an outer unshielded shell and was quenched in the Transition series; the observed moment being due to spin only.
Results for Iron, Cobalt and Nickel were reasonably satisfactory, although small deviations have been observed. As the outer electronic configurations of the triads Ruthenium, Rhodium and Palladium, and Osmium, Iridium and Platinum are similar, it would be expected that a theory which accounted for the Iron triad, would also account for the two later triads. However, this is not the case and some revised theory is necessary.
