GENERALIZATION OF THE PAIR APPROXIMATION AND ITS APPLICATION TO (ZN1-XMNX)3AS2

By taking into account the results of recent studies of (Zn1-xMnx)3As2 (ZMA), which is an example of a II-V diluted magnetic semiconductor (DMS) with a very complicated tetragonal crystal structure, we have generalized the pair-approximation model, widely used to analyze the magnetic behavior of II-VI DMS's, for an arbitrary structure. We have subsequently applied our model, which may be called the generalized pair approximation, to reinterpreting the results of magnetic measurements obtained for ZMA. Based on theoretical works that treat the Mn-Mn interaction in DMS's as a sum of superexchange and the Bloembergen-Rowland (BR) mechanism, we have been able to obtain satisfactory agreement between our approach and experiment by introducing only two adjustable parameters, in spite of the complexity of the crystal structure of ZMA. These parameters are the first nearest-neighbor exchange constants for both mechanisms and they have been found to be equal to -53 and -11 K for superexchange and the BR exchange, respectively.