Theoretical calculation for the Fermi surface structures of CeSb in the ferromagnetic and ferrimagnetic AFF1 phases

The Fermi surface structures of CeSb in the ferromagnetic (F) phase and in the ferrimagnetic AFF1 phase are studied. The pf mixing model explains vari ous anomalous magnetic properties of this compound and predicts the beta 4 hole surface in the F phase. But the beta 4 surface in the previous calcula tion has the discrepancy from the observations of the de Haas-van Alphen ef fects. The fully polarized \ j = 5/2, j(z) = 5/2) state has been assumed as the occupied orbit of the 4f state. We show that the discrepancy is largel y reduced when the occupied 4f state has a little more amplitude of a Gamma (7) component than the fully polarized state, although unresolved deviation still remains. The calculated Fermi surfaces of the AFF1 phase explain wel l the experimental results. The beta(4) surface in the F phase changes to t he folded and open structure in the AFF1 phase showing new extremal areas. It is shown that the beta(4) surface has a very anisotropic mass enhancemen t factor, which is consistent with the pf mixing model. As the mechanism to improve the agreement, various types of many body effects are discussed.