Physics of low-carrier system detected by neutron and X-ray scattering: Ce-monopnictides case

The origin of the unusual magnetic properties of Ce-monopnictide, CeX (X = P,As,Sb,Bi), whose carrier density is very low, is discussed on the basis o f the physical picture obtained from recent neutron and X-ray scattering ex periments. It is revealed that the unusual properties of the compounds orig inate from the appearance of T-8-like Ce ions, the moment value of which is about 2 mu(B), among Ce ions with Gamma(7) crystal field ground state. The 2 mu(B) Ce ions appear in the form of ferromagnetic sheets of (0 0 1) plan es, which form stacking magnetic structures of various sequences with sandw iching Gamma(7) Ce planes depending on the carrier density. The formation o f the ferromagnetic sheets of 2 mu(B) Ce in the Gamma(7) Ce lattice is ascr ibed to the combined effects of strong p-f mixing and carrier localization due to the low-carrier density. (C) 2000 Elsevier Science B.V. All rights r eserved.