Interplay between crystal field splitting and Kondo effect in CeNi₉Ge_4−xSi_x

Abstract

The pseudo-ternary solid solution CeNi(9)Ge(4-x)Si(x) (0 ≤ x ≤ 4) has been investigated by means of x-ray diffraction, magnetic susceptibility, specific heat, electrical resistivity, thermopower and inelastic neutron scattering studies. The isoelectronic substitution of germanium by silicon atoms causes a dramatic change of the relative strength of competing Kondo, RKKY and crystal field (CF) energy scales. The strongest effect is the continuous elevation of the Kondo temperature T(K) from approximately 3.5 K for CeNi(9)Ge(4) to about 70 K for CeNi(9)Si(4). This increase of the Kondo temperature is attended by a change of the CF level scheme of the Ce ions. The interplay of the different energy scales results in an incipient reduction of the ground state degeneracy from an effectively fourfold degenerate non-magnetic Kondo ground state with unusual non-Fermi-liquid features of CeNi(9)Ge(4) to a lower one, followed by an increase towards a sixfold, fully degenerate ground state multiplet in CeNi(9)Si(4) (T(K) ∼ Δ(CF)).

Interplay between disorder-driven non-Fermi-liquid behavior and magnetism in the Ce0.24La0.76Ge compound

“…Also, it is observed that magnetic hysteresis is absent in both of these compounds (not shown). properties in low temperature region [32,34]. For La_0.4 compound, it is noted that resistivity rises around T I , followed by a maximum around T II (upper inset of Fig.2 (b)).…”

“…For La_0.4 compound, a peak is observed around T I followed by a weak anomaly around T II (shown by an arrow). The curve is featureless for La_0.76 compound because the transition temperature is shifted below 1.8 K. For both compounds, it is noted that with decreasing temperature C increases and attains broad maxima around 155 K. Such feature possibly arises due to the presence of incoherent Kondo scattering along with the CEF effect[32]. Upper inset ofFig.…”

Symmetry and correlations underlying hidden order inURu2Si2

“…The full moment degeneracy is preserved by the high-temperature Kondo scattering, which serves to effectively quench the local crystal-field splitting. Such an effect is observed in the case of CeNi 9 Si 4 , which has a full 6-fold degenerate ground state when chemical tuning sets T K = 70 K, comparable to the crystal-field splitting 46 . The large low-temperature J in URu 2 Si 2 gives rise to a strong magnetic excitation spectrum and, of course, a large configurational degeneracy.…”

Crystal fields and Kondo effect: Specific heat for Cerium compounds

“…We now introduce the deviations from the strong field limit as ( ) ( / ) ,1 5 r r r n n n g g A T u r = →∞ + ≤ ≤ (7) and rewrite equations (5) in terms of ( ) r n u :…”

“…Kondo temperatures given in eq. (6) and(7) of ref. 11 are reproduced numerically by the present calculations.…”