Magnetic Properties of Divalent Europium Compounds

摘要

Three objectives have been achieved. The initial problem was the preparation of materials. In the beginning, it was difficult to prepare powder samples which showed less than 5% second phase and single crystals were unavailable; by the end of the contract, the production of good powder samples was routine, while large single crystals of EuO and smaller single crystals of the other compounds could be grown. The experimental measurements made included magnetization, susceptibility, specific heat, nuclear magnetic resonance, and electron paramagnetic resonance. Theoretical treatments showed that all of the experimental results could be interpreted on the basis of the simple Heisenberg model with two exchange interactions; the nearest neighbor exchange interaction is positive and decreases rapidly with increasing lattice parameter, while the next nearest neighbor exchange interaction is negative and increases in magnitude rather slowly with increasing lattice parameter. These combined experimental (physical and chemical) and theoretical investigations have provided a critical test of the Heisenberg model for insulators. (Author)