Magnetic ordering inCeM2Si2(M=

Abstract

We report the results of neutron-diffraction experiments on CeM2Si2 (M =Ag, Au, Pd, Rh) which were performed to explore the role of valence fluctuations and 4f hybridization in the magnetic ordering of cerium compounds. All four order antiferromagnetically, the first three exhibiting structures consisting of ferromagnetic layers with moments perpendicular to the layers, which are believed to be characteristic of 4f 4f inte-ractions mediated through hybridization with conduction electrons. CePd2Si2 has an anomalously small moment (0.62pq) in the ordered state. CeAg2Si2 exhibits an incommensurate longitudinal, static magnetization wave with moment and propagation direction along the a axis. The fourth compound, CeRh2Si2, has the highest known transition temperature (39 K) reported for cerium ordering; it exhibits another second-order transition at 27 K to a complex commensurate structure with modulated moments. The results are discussed in terms of the effects that 4f hybridization can have on ordering.

Lattice disorder and magnetism in f-electron intermetallics

“…In any case, the measured single-site u 2 's at 20 K remain low: 0.00036(1)Å 2 , 0.003(1)Å 2 , and 0.0029(3)Å 2 for the Ce, Rh/Ru and Si sites, respectively. All other fit parameters are consistent with previous Rietveld results on the end members of the Ce(Rh 1−x Ru x ) 2 Si 2 series [19].…”

Magnetic excitations in heavy-fermionCePd2Si2

“…5,6 Below the Néel temperature T N ϭ8.5 K, antiferromagnetic order develops with a propagation vector kϭ(1/2,1/2,0) and the ordered moments lying in the basal plane. 7,8 The ordered moment of 0.66 B is reduced by crystal-field effects and possibly by Kondo screening as well. Kondo-type spin fluctuations develop at low temperatures and give rise to an increase in the density of states at the Fermi level, as manifested in the strong renormalization of the effective mass observed in low-temperature specific-heat measurements, where the linear electronic term is ␥Ӎ250 mJ mol Ϫ1 K Ϫ2 .…”

Variation of ground states in CePt2-xAuxSi2 compounds (x = 0, 1, 2)

“…From neutron-scattering work reported in ref. 10, a simple antiferromagnetic structure of type I was deduced and the ordered moment per Ce ions was found to be 1.3 I.tB/Ce, a value that may well correspond with possible wave-functions of the lowest doublet state.…”