Crystalline Electric Field Level Scheme Research Articles

Crystal electric field level scheme leading to giant magnetocaloric effect for hydrogen liquefaction

In recent years, magnetic refrigeration has attracted considerable attention for hydrogen liquefaction. Most materials used for magnetic refrigeration contain heavy rare earth ions with complex crystalline electric field energy splittings, whose effect on the magnetic entropy change ΔSM has not been systematically studied. In particular, the theoretical upper limits of ∣ΔSM∣ for general heavy earth cases are unknown. Here, we show that the crystalline electric field level schemes result in a large ΔSM for general heavy rare earth cases. We provide a specific example of the magnetic refrigeration material HoB2 using inelastic neutron scattering experiments combined with mean-field calculations with crystal field splitting and exchange interactions. The relationship between ΔSM and crystal field parameters presented in this study can be useful for developing compounds with a large ∣ΔSM∣ and advancing the design of magnetic refrigeration materials.

Electronic and structural properties of RbCeX2 (X2: O2, S2, SeS, Se2, TeSe, Te2)

Triangular lattice delafossite compounds built from magnetic lanthanide ions are a topic of recent interest due to their frustrated magnetism and realization of quantum disordered magnetic ground states. Here we report the evolution of the structure and electronic ground states of $\mathrm{RbCe}{X}_{2}$ compounds, built from a triangular lattice of ${\mathrm{Ce}}^{3+}$ ions, upon varying their anion character $({X}_{2}={\mathrm{O}}_{2}$, ${\mathrm{S}}_{2}, \mathrm{SeS}, {\mathrm{Se}}_{2}, \mathrm{TeSe}, {\mathrm{Te}}_{2})$. This includes the discovery of a new member of this series, ${\mathrm{RbCeO}}_{2}$, that potentially realizes a quantum disordered ground state analogous to ${\mathrm{NaYbO}}_{2}$. Magnetization and susceptibility measurements reveal that all compounds manifest mean-field antiferromagnetic interactions and, with the exception of the oxide, possess signatures of magnetic correlations onset below 1 K. The crystalline electric field level scheme is explored via neutron scattering and ab initio calculations in order to model the intramultiplet splitting of the $J=5/2$ multiplet. In addition to the two excited doublets expected within the $J=5/2$ manifold, we observe one extra local mode present across the sample series. This added mode shifts downward in energy with increasing anion mass and decreasing crystal field strength, suggesting a long-lived anomalous mode endemic to anion motion about the ${\mathrm{Ce}}^{3+}$ sites.

Inelastic neutron scattering study of crystalline electric field excitations in a cubic compound PrMgNi4

We performed inelastic neutron scattering experiments on PrMgNi4 with the cubic MgSnCu4-type structure. The magnetic excitations were observed at 1.1, 2.5, 5.9, 10.7, and 11.7 meV. Since the energy of the excitations is constant for | Q | < 5 Å−1, they are ascribed to the crystalline electric field (CEF) excitations of the Pr3+ ions. We adopted CEF parameters of W = −3.3 K and x = 0.8 for the cubic T d point group to reproduce the strong excitations at 1.1, 10.7, and 11.7 meV. The calculated CEF level scheme reveals the Γ3 doublet ground state with the quadrupolar degrees of freedom and the excited states of Γ4 triplet (1.4 meV), Γ1 singlet (3.4 meV), and Γ5 triplet (13.5 meV). This scheme, however, does not explain the observed two excitations at 2.5 and 5.9 meV. These additional excitations may arise from splitting of the doublet by symmetry lowering due to excess Mg atoms occupying the Pr sites. This splitting is probably responsible for the absence of the long-range quadrupole order in PrMgNi4.

Magnetic properties and signatures of ordering in triangular lattice antiferromagnet KCeO2.

The magnetic ground state and the crystalline electric field level scheme of the triangular lattice antiferromagnet are investigated. Below mK, develops signatures of magnetic order in specific heat measurements and low energy inelastic neutron scattering data. Trivalent ions in the local environment of this compound exhibit large splittings among the lowest three Kramers doublets defining for the free ion the sextet and a ground state doublet with dipole character, consistent with recent theoretical predictions in M. S. Eldeeb et al. Phys. Rev. Materials 4, 124001 (2020). An unexplained, additional local mode appears, and potential origins of this anomalous mode are discussed.

Magnetic order inNd2PdSi3investigated using neutron scattering and muon spin relaxation

The rare-earth based ternary intermetallic compounds $R_2TX_3$ ($R$ = rare-earth, $T$ = transition-metal, $X$ = Si, Ge, Ga, In) have attracted considerable interest due to a wide range of interesting low temperature properties. Here we investigate the magnetic state of Nd$_{2}$PdSi$_{3}$ using neutron diffraction, muon spin relaxation ($\mu$SR) and inelastic neutron scattering (INS). This compound appears anomalous among the $R_{2}$PdSi$_{3}$ series, since it was proposed to order ferromagnetically, whereas others in this series are antiferromagnets. Although some members of the $R_2TX_3$ series have been reported to form ordered superstructures, our data are well described by Nd$_{2}$PdSi$_{3}$ adopting the AlB$_2$-type structure with a single Nd site, and we do not find evidence for superlattice peaks in neutron diffraction. Our results confirm the onset of long range magnetic order below $T_0=17$~K, where the whole sample enters the ordered state. Neutron diffraction measurements establish the presence of a ferromagnetic component in this compound, as well as an antiferromagnetic one which has a propagation vector $\mathbf{k_2}=(1/2,1/2,1/4-\delta)$ with a temperature dependent $\delta\approx0.02-0.04$, and moments orientated exclusively along the $c$-axis. $\mu$SR measurements suggest that these components coexist on a microscopic level, and therefore the magnetic structure of Nd$_{2}$PdSi$_{3}$ is predominantly ferromagnetic, with a sinusoidally modulated antiferromagnetic contribution which reaches a maximum amplitude at 11~K, and becomes smaller upon further decreasing the temperature. INS results show the presence of crystalline-electric field (CEF) excitations above $T_0$, and from our analysis we propose a CEF level scheme.

Suppression of long-range ferromagnetic order in the CexLa1−xTiGe3 system

We report specific heat, magnetization, and resistivity measurements on single crystals of ${\mathrm{Ce}}_{x}{\mathrm{La}}_{1\ensuremath{-}x}{\mathrm{TiGe}}_{3}$ systems. When the Ce concentration $x$ is increased, the system changes from a single-ion Kondo system for $x=0.05$ into a ferromagnetic Kondo lattice for $x=1$, where the magnetic part of electrical resistivity reveals a single-ion scaling with $x$. The isoelectric substitution of Ce by La atoms causes a change of the relative strength of competing energy scales of Kondo and RKKY interaction and crystalline electric field (CEF). The substitutions induce the continuous evolution of the Kondo temperature ${T}_{K}$ and the linear variation of ferromagnetic ordering temperature ${T}_{c}$, which are accompanied by a change of the CEF level scheme of the Ce ions. The composition-temperature ($x\text{\ensuremath{-}}T$) phase diagram for ${\mathrm{Ce}}_{x}{\mathrm{La}}_{1\ensuremath{-}x}{\mathrm{TiGe}}_{3}$ is constructed by a combination of magnetization, specific heat, and resistivity measurements. The ferromagnetic ordering temperature is linearly suppressed as $x$ decreases and vanishes near the critical concentration ${x}_{c}=0.1$, but conventional quantum criticality is absent near ${x}_{c}$. The specific heat measurement for $x=0.05$ reveals the power law increase of the electronic specific heat coefficient ${C}_{m}/T\ensuremath{\propto}1/T$ with a large value of $\ensuremath{\sim}3.5$ J/mol ${\mathrm{K}}^{2}$ at $T=0.4\phantom{\rule{0.28em}{0ex}}\mathrm{K}$. The magnetic susceptibility for $x=0.05$ also shows a power law dependence $\ensuremath{\chi}(T)\ensuremath{\propto}1/T$ below 10 K.

Magnetically Ordered State and Crystalline-Electric-Field Effects in SmBe13

The physical properties of single-crystalline SmBe$_{13}$ with a NaZn$_{13}$-type cubic structure have been studied by electrical resistivity ($\rho$), specific heat ($C$), and magnetization ($M$) measurements in magnetic fields of up to 9 T. The temperature ($T$) dependence of $\rho$ shows normal metallic behavior without showing the Kondo -ln$T$ behavior, suggesting the weak hybridization effect in this system. Analyses of the temperature dependence of $C$ suggest that the Sm ions of this compound are trivalent and that the crystalline-electric-field (CEF) ground state is a $\Gamma_8$ quartet with a first-excited state of a $\Gamma_7$ doublet located at the energy scale of $\sim$ 90 K. Mean-field calculations based on the suggested CEF level scheme can reasonably well reproduce the $T$ dependence of magnetic susceptibility ($\chi$) below $\sim$ 70 K. These results in the paramagnetic state strongly indicate that the 4$f$ electrons are well localized with the Sm$^{3+}$ configuration. At low temperatures, the 4$f$ electrons undergo a magnetic order at $T_{\rm M}$ $\sim$ 8.3 K, where $\chi$($T$) shows an antiferromagnetic-like cusp anomaly. From the positive Curie--Weiss temperature obtained from the mean-field calculations and from a constructed magnetic phase diagram with multiple regions, we discussed the magnetic structure of SmBe$_{13}$ below $T_{\rm M}$, by comparing with other isostructural MBe$_{13}$ compounds showing helical-magnetic ordering.

Ferromagnetism in orthorhombic RAgAl3 (R = Ce and Pr) compounds

We present a detailed study on magnetic, thermodynamic and transport properties of polycrystalline RAgAl3(R = Ce and Pr) compounds. Both compounds crystallize in orthorhombic structure, which is distorted from the tetragonal BaAl4 structure with the space group Cmcm. Heat capacity measurement indicates the bulk magnetic ordering of the compounds. CeAgAl3 and PrAgAl3 order ferromagnetically at TC=3.8K and 5.8K, respectively as it was confirmed from magnetic measurements. CeAgAl3 exhibits heavy fermion behaviour. The Schottky behaviour in heat capacity data was observed in both compounds. The crystalline electric field (CEF) analysis of the magnetic parts of heat capacity of CeAgAl3 and PrAgAl3 yielded to a CEF level scheme with three doublets and nine singlets and with an overall splitting of 51K and 180K, respectively. Fit yielded a magnetic doublet state for CeAgAl3, whereas for PrAgAl3 a pseudo-doublet ground-state with an energy difference of 15K has been obtained. The resistivity measurements display a low temperature drop at the magnetic ordering temperature of the compounds. Negative magnetoresistance (MR) due to the ferromagnetic ordering has been observed for both Ce and Pr compounds.

Pr- and La-doping effects on the magnetic anisotropy in the antiferromagnetic phase of Kondo semiconductorCeRu2Al10

We have studied the Pr- and La-doping effects on the magnetic anisotropy in the antiferro-magnetic (AFM) phase of ${\mathrm{CeRu}}_{2}{\mathrm{Al}}_{10}$. The crystalline electric field (CEF) splitting in ${\mathrm{PrRu}}_{2}{\mathrm{Al}}_{10}$ was found to be as large as $\ensuremath{\sim}800$ K with a singlet ground state. In ${\mathrm{Ce}}_{1\ensuremath{-}x}{\mathrm{Pr}}_{x}{\mathrm{Ru}}_{2}{\mathrm{Al}}_{10}$, the CEF level scheme of the Pr ion is not changed with $x$. The AFM moment (${m}_{\mathrm{AF}}$) is rotated from $c$ to $b$ axis in both systems at ${x}_{c}^{\mathrm{sr}}\ensuremath{\sim}0.03$ and $\ensuremath{\sim}0.07$ for Ln=Pr and La, respectively. As the ionic radius of La and Pr is larger and smaller than that of Ce, respectively, these results indicate that the chemical pressure effect is not associated with the rotation of ${m}_{\mathrm{AF}}$, but is caused by the suppression of the $c\ensuremath{-}f$ hybridization originating from the decrease of $4f$ electrons of Ce ions by Ce-site substitution. Since a small amount of Pr or La doping changes easily the magnetization easy axis of all the moments on Ce sites, the origin of the magnetic anisotropy is not the local single ion effect but the bandlike effect through the anisotropic $c\ensuremath{-}f$ hybridization. The magnetic phase diagrams of ${\mathrm{Ce}}_{1\ensuremath{-}x}{\mathrm{Ln}}_{x}{\mathrm{Ru}}_{2}{\mathrm{Al}}_{10}$ indicate that above ${x}_{c}^{\mathrm{sr}}$, the AFM order with ${m}_{\mathrm{AF}}\ensuremath{\parallel}b$ continues to exist up to ${x}_{c}$, which is $\ensuremath{\sim}0.4$ and $\ensuremath{\sim}0.6$ in Ln=Pr and Ln=La, respectively. This indicates that even in the sample with an AFM transition temperature (${T}_{0}$) near ${x}_{c}$, the anisotropic $c\ensuremath{-}f$ hybridization dominates the AFM order. A large positive transverse magnetoresistance is seen below ${T}_{0}$, but a very small one above ${T}_{0}$. Together with the results of Hall resistivity and the observation of Shubnikov--de Haas oscillation, we propose that there exist large Fermi surfaces above ${T}_{0}$ and small ones below ${T}_{0}$. A gap is opened by the AFM order on almost the area of the large Fermi surface, and small Fermi surfaces are constructed below ${T}_{0}$, although we do not know the mechanism, which might be specific to the AFM order in Kondo semiconductors. The largest suppression of the magnetic scattering below ${T}_{0}$ is observed for the current $I\ensuremath{\parallel}a$ and the smallest one for $I\ensuremath{\parallel}b$. This anisotropy may be associated with the anisotropic $c\ensuremath{-}f$ hybridization, which may contribute to the anisotropic magnetic scattering of the conduction electron below ${T}_{0}$.

Marked Change in the Ground State of CeRu2Al10Induced by Small Amount of Rh Substitution

We have investigated the marked change in the magnetic properties of CeRu2Al10 induced by a small amount of Rh substitution [Ce(Ru0.95Rh0.05)2Al10]. The magnetic susceptibility along the \(a\)-axis (χa) shows a large decrease with decreasing temperature after showing a sharp peak at \(T_{0}=24\) K and the high field magnetization for the magnetic field along the \(a\)-axis exhibits a spin-flop transition at \({\sim}13\) T. These indicate that the antiferromagnetic (AFM) order where the AFM moment is parallel to the \(a\)-axis takes place, which is consistent with the anisotropy of χa>χc>χb in the paramagnetic region, being different from the AFM order in CeRu2Al10. These results were analyzed by mean field calculation for the two-sublattice model using the crystalline electric field level scheme by Strigari et al. [Phys. Rev. B 86 (2012) 081105]. On the basis of both experimental and calculated results, we conclude that, by a small amount of Rh substitution with one extra \(4d\) electron, the large \(c\)–...

Magnetic phase diagram and crystalline electric field of NdRu2Al10 single crystal

We measured specific heat of NdRu2Al10 single crystal under magnetic field along a-axis in order to investigate basic physical properties of this compound. We found three anomalies at T1 ~ 2.4 K, T2 ~ 1.2 K and T3 ~ 0.9 K in the temperature dependence of specific heat. These anomalies are attributed to antiferromagnetic order. In addition, we observed a Schottky-type anomaly, which reflects splitting of crystalline electric field (CEF). The entropy reaches Rln2 just above T1 and almost reaches Rln10 at room temperature. These results indicate that these three phase transitions occur in a doublet ground state and that all CEF levels of J = 9/2 are below 300K. The results of specific heat are consistent with the CEF level scheme proposed by magnetization measurement.

Crystalline Electric Field Effects and Hidden Order in URu2Si2

We show that an antiferro-octupole order of E u ( x ( y 2 - z 2 ), y ( z 2 - x 2 )) symmetry accounts for the rotational symmetry (RS) reduction of the basal plane magnetic susceptibility in the hidden order (HO) phase of URu 2 Si 2 . We determine the crystalline electric field level scheme with lower singlet-doublet levels, which can stabilize the E u octupole order, as well as the quadrupole order of E g ( y z , z x ) symmetry. Both orders can explain the RS reduction, but the octupole order breaks the time reversal symmetry, in agreement with the ligand NMR measurements, while the quadrupole order does not. Consequently, the E u octupole order is favorable for the HO of URu 2 Si 2 .

Transport, thermal, and magnetic properties in heavy-fermion superconductor Ce 2CoIn 8

We have grown high purity single crystals of Ce 2CoIn 8 using the self-flux technique, and have investigated its transport, thermal, and magnetic properties, including the anisotropic features. Single crystals of Ce 2CoIn 8 were grown in the lower temperature region to avoid the formation of un-wanted phases such as CeCoIn 5 and CeIn 3 impurities. The results of the structural and physical measurements imply that the present single crystals have high purity. The electrical resistivity and specific heat measurements demonstrate that Ce 2CoIn 8 has a superconducting ground state with a distinct non-Fermi liquid character. This indicates that the superconductivity in Ce 2CoIn 8 arises out of the verge of the underlying quantum critical instability mediated by the antiferromagnetic correlations. Additionally, we investigate the crystalline electric field (CEF) energy scheme based on the temperature dependence of the specific heat and the anisotropic features in the susceptibility. We propose one of the CEF level schemes calculated on the basis of the CEF model that the first and second CEF states are located at Δ 1 = 82 K and Δ 2 = 102 K above the ground state doublet, respectively.

La substitution effect and hyperfine-enhancedP141rnuclear spin dynamics inPrPb3:L139aNMR study inPr0.97La0.03Pb3

$^{139}\text{L}\text{a}$ NMR studies have been performed on ${\text{PrPb}}_{3}$ substituted with 3% La. The temperature dependence of the local magnetic susceptibility around La ions has been extracted from the $^{139}\text{L}\text{a}$ Knight shift. These data show that the nonmagnetic ${\ensuremath{\Gamma}}_{3}$ crystalline-electric-field (CEF) ground state (GS) is preserved even at the nearest neighboring Pr ions, although their CEF level scheme is slightly modified due to the La substitution. On the other hand, the temperature dependence of the nuclear spin-lattice relaxation rate $1/{T}_{1}$ is found to be well reproduced by assuming the same CEF level scheme over a wide temperature range. However, $1/{T}_{1}$ shows a strong upturn below 10 K, which is not expected from the nonmagnetic CEF GS. We show that the low-temperature anomaly can be quantitatively understood in terms of a cross-relaxation process between $^{141}\text{P}\text{r}$ and $^{139}\text{L}\text{a}$ nuclear spins. Analysis of the cross-relaxation process reveals strong nuclear spin-spin coupling among the $^{141}\text{P}\text{r}$ nuclei, which we suggest is enhanced by a hyperfine mechanism of Pr ions and then mediated by relatively large indirect magnetic coupling between them.

Neutron scattering study on U-dichalcogenides

We will report the results of our recent inelastic neutron scattering study on β-US2. This compound shows a semi-metallic or narrow gap semi-conducting behaviour at room temperature. A clear exponential up-turn of the resistivity in the order of ~106 Ωcm has been observed below 100 K. We found a sharp inelastic peak at the excitation energy of about 7 meV at 8 K. The Q-dependence of the peak intensity is in good agreement with the magnetic form factor of U4+ ion and no clear dispersion relation has been observed. Therefore we concluded that this is a crystalline electric field (CEF) excitation peak. The excitation energy is in good agreement with the CEF level scheme obtained from the susceptibility data. The CEF peak intensity decreases with increasing temperature and becomes much weaker than the calculated temperature factor expected from the CEF level scheme. Furthermore a quasi-elastic response appears, and coexists with a broadened CEF peak at higher temperatures. The quasi-elastic component is not due to phonon, because the temperature dependence of the intensity is inconsistent with calculation. We concluded that this quasi-elastic response is a hybridization effect of U-5f electrons with, most likely, p-electrons of sulfur. It is highly interesting that the energy scale of the CEF peak (~7 meV) is very close to the conduction gap (90K), and the quasi-elastic component appears above the characteristic temperature of about 100 K. Our data strongly suggest that the crossover of 5f character plays an import role for the metal-insulating transition in β-US2.

Low-temperature magnetization of PrMg3 with a Γ3 non-Kramers doublet ground state

Magnetization of a single crystal of cubic PrMg3 with a Γ3 non-Kramers doublet ground state has been examined at low temperatures down to 60 mK in fields up to 8.5 T. The 4f-electronic contribution of the magnetic susceptibility χ4f(T) is significantly enhanced over the expected Van-Vleck behavior and shows like temperature variation in a finite region 0.3 ≤ T ≤ 2.5 K. We argue that this enhancement in χ4f(T) originates from the Γ3 ground state and hybridization with conduction electrons. No such unusual temperature variation is observed in χ4f(T) of a tetragonal compound PrB2C2 which has a singlet ground state in the crystalline electric field level scheme.

Anomalous properties in the low-carrier ordered phase ofPrRu4P12: Consequence of hybridization between conduction andPr 4felectrons

The low-carrier ordered phase below the metal-non-metal transition temperature ${T}_{\text{MI}}\ensuremath{\simeq}63\text{ }\text{K}$ of ${\text{PrRu}}_{4}{\text{P}}_{12}$ is explored by probing magnetoresistance, magnetic susceptibility, thermoelectric power, and Hall effect on high-quality single crystals. All the measured properties exhibit the signature of decimation of the Fermi surface below ${T}_{\text{MI}}$ and anomalous behaviors below 30 K including a large thermoelectric power $\ensuremath{\sim}\ensuremath{-}200\text{ }\ensuremath{\mu}\text{V}/\text{K}$ and a giant negative magnetoresistance (93% at $\ensuremath{\sim}0.4\text{ }\text{K}$). The results indicate an additional structure below 30 K and a semimetal-like ground state. The observed anomalous behaviors are most likely associated with the role of $c\text{\ensuremath{-}}f$ hybridization between conduction electrons and $\text{Pr}\text{ }4f$ electrons, whose crystalline electric field level schemes show drastic change below ${T}_{\text{MI}}$.

Crystal field effect on specific heat and magnetic susceptibility of single crystals of CexLa1-xPt3Si

Measurements of the temperature dependence of magnetic susceptibility and specific heat down to ∼ 1.5 K were carried out to investigate the crystalline electric field (CEF) state of CePt3Si. In the Ce-dilute region (x = 0.05), a single crystal could be prepared successfully by the Czochralski pulling method. The results in dilute alloys indicate that the first excited CEF level is well separated from the ground state doublet; the CEF level schemes with doublets lie at 0, 139, and 176 K.

Crystalline electric field effects inPrNi2B2C: Inelastic neutron scattering

${\text{PrNi}}_{2}{\text{B}}_{2}\text{C}$ as a member of the borocarbide series is characterized by antiferromagnetic order below ${T}_{N}=4\text{ }\text{K}$ and the absence of superconductivity (at least down to 100 mK). There are two effects responsible for the absence of superconductivity in ${\text{PrNi}}_{2}{\text{B}}_{2}\text{C}$. These are the strong conduction electron--Pr moment interaction and a comparatively lower density of states. We studied the crystalline electric field (CEF) excitations and excitons in this compound by inelastic neutron scattering. The CEF level scheme obtained from these data comprises a singlet ground state, a doublet at 1 meV, and further higher levels at 5.2, 24.3 (doublet), 25.1, 29.4, and 31.5 meV. Large dispersion was found for the 1 meV excitation and explained theoretically taking into account magnetic exchange interactions. The calculated crystal-field parameters explain satisfactorily the neutron spectra as well as the heat-capacity and magnetic-susceptibility data. This leads to the conclusion that ${\text{PrNi}}_{2}{\text{B}}_{2}\text{C}$ can be described by the standard model of rare-earth magnetism. Thus the heavy-fermion concept, suggested by some groups earlier in literature, is not the cause of the suppression of superconductivity. Excitation spectra of the diluted series ${\text{Pr}}_{1\ensuremath{-}x}{\text{Y}}_{x}{\text{Ni}}_{2}{\text{B}}_{2}\text{C}$ were also investigated. No drastic changes in the CEF level scheme have been observed in these compounds. Hence the CEF level scheme of the full compound, i.e., ${\text{PrNi}}_{2}{\text{B}}_{2}\text{C}$, is reasonably valid for these samples too. The superconducting-transition temperature ${T}_{C}\ensuremath{\sim}15.5\text{ }\text{K}$ for ${\text{YNi}}_{2}{\text{B}}_{2}\text{C}$ decreases linearly with decreasing Y concentration $x$. Samples with $x\ensuremath{\le}0.65$ do not exhibit superconductivity down to 2 K.

Crystalline electric fields and the ground state of YbRh 2Si 2 and YbIr 2Si 2

We have constructed the crystalline electric field (CEF) splitting of the energy levels of Yb 3+ (4f 13) in the clean intermetallic compounds YbRh 2Si 2 and YbIr 2Si 2. The data of measurements using methods of inelastic neutron scattering, electron spin resonance, and Mössbauer spectroscopy, together with relevant structural, thermodynamic, and magnetic properties, were used as input to calculations of the CEF level schemes in these non-Fermi-liquid systems. The experimental data of both compounds are found to be well explained on the basis of the CEF 4f-schemes with the Γ t 6 - ( 1 ) ground state symmetry.