The Magnetic Properties of Isolated Ferromagnetic Atoms

In order to obtain a better knowledge of the elementary atomic magnet, its behavior when surrounded by non-magnetic atoms rather than by other magnetic ones has been studied. For this purpose alloys of 90% and 95% platinum with the remainder cobalt and nickel, respectively, have been investigated. Only the cobalt alloys were found magnetic. The magnetic moment per cobalt atom being greater than for pure cobalt, the platinum may contribute to the magnetism. Variation of magnetization with temperature and the Curie points have been measured, the latter falling rapidly as the cobalt content decreased. Various hysteresis loops, showing the relation between the magnetization and applied magnetic force have also been obtained, the hysteresis being less for the 10% Co alloy, after annealing. In the harddrawn state, however, the hysteresis and Curie points are considerably higher. The results are shown to be in agreement with Heisenberg's theory of ferromagnetism.