A ferrimagnetic model for the exchange constant in magnetic bubble garnets

The exchange constant, A, for a magnetic bubble garnet is calculated using a ferrimagnetic molecular field model. This model predicts the temperature dependence of A for a given material as a function of Néel temperature and nonmagnetic ion substitution into the tetrahedral and octahedral sites of the garnet crystal lattice. Most of the available data for A from representative bubble garnets yields good agreement with the calculations. Approximate determination of A from the model should be useful for characterizing new magnetic bubble materials as a function of temperature.