Critical neutron scattering in CeSb

Abstract

Diffuse critical neutron scattering above the antiferromagnetic first-order phase transition has been observed in the cerium monopnictide CeSb. Whereas the long-range ordering below T_N=16.4K has type-A2/3 structure with superlattice peaks at q₀=(2 pi / alpha ) (0,0,²/₃) the fluctuations are of type-I antiferromagnetic (AF/I) structure and disappear when the long-range ordering occurs. This frustration indicates that the system is near a Lifshitz point. The longitudinal spin correlation is anisotropic and the transverse fluctuations are unobservably small. The authors analysed the critical behaviour by a mean-field treatment of a Hamiltonian that includes strong cubic anisotropy.