Calculation of magnetic moments in Ho2C3 nanocrystals

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Abstract
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 explain the reduced magnetic moments, relative to free ion values, measured by dc SQUID magnetometry for Ho2C3nanocrystals. Crystal‐field splittings of the rare‐earth ion in a particular symmetry site are determined by the operator equivalent method. Using the eigenvalues and eigenfunctions of the crystal‐field Hamiltonian, the effective magnetic moment is then determined. For Ho3+ ions in Ho2C3, this method predicts a reduced magnetic moment, but the degree of reduction depends on the energy‐level splittings and, therefore, the temperature. This magnetic moment is compared with previous experimental results, and the implications of the formal carbon charge, screening, and temperature are discussed.