Abstract
The exchange-energy parameter for conduction-band electrons in was determined at K for . For this range of , is independent of and has the value (258±5) meV. These results were obtained by comparing Raman scattering data for the spin splitting of donor electrons with magnetization data on the same crystals. The Raman data were obtained for , and the magnetization data were taken for . The magnetization was measured at temperatures between 1.5 and 4.2 K in magnetic fields up to 83 kOe. These data were fit to a parametrized Brillouin function. One of the fitting parameters gave an effective concentration of magnetically active ions. The second fitting parameter was a measure of the average antiferromagnetic interaction between the Mn spins. The low-field magnetic susceptibility was fit to a Curie-Weiss law, which yielded the analogous parameters and for low fields. As increased from 0.05 to 0.3, the fraction of magnetically active ions, , decreased from 0.6 to 0.1, and increased from 1.5 to 7 K. These trends are caused by the increase in the average antiferromagnetic interaction between the Mn spins as the average distance between them decreases with increasing . Results of spin-flip Raman scattering from donor-bound electrons show that the Zeeman splitting of the donor's energy is large ( meV) for fields above 40 kOe. The splitting is approximately proportional to the magnetization, except at low where there is an additional contribution due to the difference between the local magnetization within the donor's orbit and the average bulk magnetization. This effect decreases for both increasing and decreasing .
- Received 23 December 1983
DOI:https://doi.org/10.1103/PhysRevB.29.5634
©1984 American Physical Society