CALCULATION OF MAGNETIC-MOMENTS IN HO2C3 NANOCRYSTALS

A general approach to the computation of effective magnetic moments in rare-earth carbides is described, and details of this calculation for Ho3+ ions in Ho2C3 are presented. This calculation is designed to exp lain the reduced magnetic moments, relative to free ion values, measur ed by de SQUID magnetometry for Ho2C3 nanocrystals. Crystal-field spli ttings of the rare-earth ion in a particular symmetry site are determi ned by the operator equivalent method. Using the eigenvalues and eigen functions of the crystal-field Hamiltonian, the effective magnetic mom ent is then determined. For Ho3+ ions in Ho2C3, this method predicts a reduced magnetic moment, but the degree of reduction depends on the e nergy-level splittings and, therefore, the temperature. This magnetic moment is compared with previous experimental results, and the implica tions of the formal carbon charge, screening, and temperature are disc ussed.