Magnetocrystalline Anisotropy and Crystal Fields in the Weak-Ferromagnet Ce4Ni3Pb4

Abstract

We report measurements of magnetization, magnetic susceptibility, specific heat, and neutron diffraction on a single crystal of the heavy fermion compound, Ce 4 Ni 3 Pb 4 , crystallizing in a trigonal structure with two inequivalent Ce sites. In the paramagnetic state, the effect of crystal electric field (CEF) leads to the easy magnetization direction along the c -axis. Magnetic Bragg peaks develop below T N =3.0 K and are indexed with a propagation vector k =[0,1,1/2]. Below T N , a spontaneous moment of 10 -3 µ B /Ce is observed only for B ⊥ c , while a metamagnetic transition is observed for B ∥ c at 1.3 T. The small spontaneous moment in the c -plane is ascribed to the slight canting of the antiferromagnetically aligned moments from the c -axis. The inelastic neutron scattering spectrum is composed of four CEF excitations at 5.3, 19, 24, and 40 meV. The peaks at 19 and 40 meV have a rather large width of 10 meV, which is three times larger than that of the others. The wide peaks are assigned to excitations from the ground state of one Ce site, the Kondo temperature of which is higher than that of the Ce ions in the other site.