Spin-1 kagome lattice antiferromagnets provide a versatile platform for exploring exotic quantum states, such as classical spin liquids and spin nematics, owing to the confluence of geometric frustration, bilinear and biquadratic interactions, and single-ion anisotropy. Here, we investigate the ground state and spin dynamics of a nearly perfect s = 1 kagome lattice, $${({\text{CH}}_{3}{\text{NH}}_{3})}_{2}{\text{NaV}}_{3}{\text{F}}_{12}$$, which hosts dominant antiferromagnetic interactions (J ≈ 10 K) alongside easy-axis anisotropy. Using a combination of thermodynamic and resonance techniques, we identify the occurrence of weak ferromagnetic ordering at TC ≈ 4 K. Singularly, even in this time-reversal symmetry-breaking state, muon spin relaxation, 23Na spin-lattice relaxation rate, and magnetic specific heat measurements collectively reveal persistent spin dynamics and intriguing gapless excitations. The observation of liquid-like correlations in the ground state establishes $${({\text{CH}}_{3}{\text{NH}}_{3})}_{2}{\text{NaV}}_{3}{\text{F}}_{12}$$ as a rare instance of the coexistence of dynamically fluctuating spins and weak ferromagnetism, raising the possibility of realizing an intriguing ground state in s = 1 kagome antiferromagnets with Ising anisotropy.

We report high-resolution synchrotron x-ray diffraction and x-ray resonant magnetic scattering (XRMS) studies of the low-temperature crystal and magnetic structures of DyCuAs, a member of theRECuAsfamily exhibiting a resistivity minimum above the antiferromagnetic (AFM) transition temperature. Synchrotron diffraction measurements reveal that DyCuAspreserves tetragonal symmetry down to low temperature within the experimental resolution, although pronounced anomalies in both lattice parametersandare observed near the AFM transition temperature,K, indicating strong magnetoelastic coupling. XRMS measurements at the Dyedge establish commensurate AFM ordering belowwith AFM Bragg peaks atq= (0, 0, 0.5). Representation analysis and calculations of the AFM Bragg peak intensities identify the magnetic structure as therepresentation, consisting of in-plane Dy moments stacked along thecaxis in asequence. The magnetic structure is therefore identical to that previously reported for SmCuAs. Comparison among DyCuAs, SmCuAs, and GdCuAssuggests that in-plane AFM order and the associated magnetic frustration on the tetragonal lattice are closely connected to the emergence of the resistivity minimum in theRECuAsfamily. At the same time, the enhanced lattice response and stronger magnetic-field sensitivity observed in DyCuAsimply that magnetoelastic and spin-orbit interactions additionally play important roles in determining the robustness of this anomalous transport behavior.

Competing magnetic interactions and frustration-induced quantum fluctuations in spatially anisotropic low-dimensional magnets often give rise to exotic magnetic phenomena, including field-induced phases. Here, we present crystal structure, magnetic susceptibility, specific heat, and electron spin resonance (ESR) measurements on polycrystalline Y2CuGe4O12, supported by density functional theory (DFT) calculations. In this compound, the Cu^2+ ions form a distorted triangular lattice with competing intraplanar ferromagnetic (J_1 ≈ 0.138 K and J_2 ≈ 0.01 K) and antiferromagnetic (J_3 ≈ -3.22 K) exchange interactions, together with a weaker interplanar antiferromagnetic coupling (J_4 ≈ -1.56 K). These interactions account for the small Curie–Weiss temperature, θ CW=-1.8 K. Despite the dominant antiferromagnetic interactions, no signature of long-range magnetic ordering is observed down to 0.4 K. Instead, broad maxima in both the magnetic susceptibility and magnetic specific heat reveal the development of short-range spin correlations, further supported by the critical ESR linewidth broadening characteristic of low-dimensional frustrated magnets. Application of an external magnetic field progressively suppresses the broad maximum in the magnetic specific heat, reflecting competition between the Zeeman and exchange energy scales, and drives the system into a field-polarized state above the saturation field, μ_0H_ s=2.6 T. In this regime, the magnetic specific heat exhibits an exponential temperature dependence, consistent with gapped magnon excitations. These results establish Y_2CuGe4O12 as a rare distorted triangular-lattice magnet in which further-neighbor exchange interactions dominate the magnetic behavior, providing a promising platform for exploring frustration-driven quantum phenomena.

The subtle interplay between competing degrees of freedom, crystal electric fields, and spin correlations can lead to exotic quantum states in 4 f ion-based frustrated triangular lattice antiferromagnets. We present the crystal structure, thermodynamic and muon spin relaxation (mu SR) studies of the 4 f ion-based frustrated magnet Ba4YbReWO12, wherein Yb3+ ions constitute a triangular lattice. The magnetic susceptibility does not show any signature of spin freezing down to 1.9 K or long-range magnetic ordering down to 0.4 K. The low-temperature Curie-Weiss fit to the inverse magnetic susceptibility data reveals a weak antiferromagnetic exchange interaction, which is corroborated by the fit of magnetic specific heat data following the J1 - J2 model with the nearest-neighbor-exchange interaction of J1 approximate to -0.197 K between the Jeff = 1/2 states of the Yb3+ moments in the lowest Kramers doublet. The lowest Kramers ground state doublet is well separated from the first excited state with a gap of Delta CEF = 278 K, as evidenced by our mu SR experiments that support the realization of Jeff = 1/2 at low temperatures. The specific heat experiments do not detect a phase transition down to 56 mK. The magnetic specific heat shows a broad maximum at 90 mK suggesting a disordered ground state with short-range spin correlations. The associated magnetic entropy release at low temperatures is consistent with that expected for the Jeff = 1/2 state. The zero-field mu SR measurements show neither the signature of spin freezing nor a phase transition, at least down to 43 mK. Our results suggest a dynamic, disordered ground state in this Jeff = 1/2 frustrated triangular lattice antiferromagnet. Ba4RReWO12 (R=rare earth) offers a viable platform to realize intriguing quantum states borne out of spin-orbit coupling and frustration.

Trillium lattices, in which magnetic ions form a three-dimensional chiral network of corner-sharing equilateral triangular motifs, offer a prominent platform to explore exotic quantum states. In this work, we report ground-state properties of the S = 5/2 trillium lattice compound K2FeSn(PO4)3 through thermodynamic, electron spin resonance (ESR), and muon spin relaxation (mu SR) experiments. Thermodynamic and ESR measurements reveal the two-step evolution of magnetic correlations across T & lowast; = 11 K, which results from an interplay between dominant antiferromagnetic Heisenberg interactions and subleading interactions. Below T & lowast;, dc and ac magnetic susceptibilities indicate weak magnetic ordering at TN 2 K under low fields, which is suppressed for mu 0H 2 T, consistent with a power-law dependence of magnetic specific heat at low temperatures. mu SR experiments confirm the dominance of persistent spin dynamics and the absence of conventional spin freezing, supporting the subtle nature of weak magnetic ordering coexisting with strong spin fluctuations. These findings underscore the potential for realizing a classical spin-liquid ground state with exotic excitations in high-spin trillium lattice systems.

The development of Kondo lattice coherence in UTe2 leads to the formation of a heavy Fermi liquid state from which superconductivity emerges at lower temperature. In Kondo lattice systems, the nuclear magnetic resonance (NMR) and muon Knight shift have proven to be particularly sensitive to the properties of the developing heavy-electron fluid. Here we report muon Knight shift measurements on high-quality UTe2 single crystals grown by a molten salt-flux method. Together with previous data from a single crystal grown by a chemical-vapor transport method, our results show the contribution of the heavy-electron liquid to the muon Knight shift increases below a crossover temperature T* ~ 30 K in accord with a universal scaling function of T/T* for heavy-fermion materials. An observed departure from this universal scaling below a temperature T ~ 12 K at certain muon stopping sites signifies a reversal of the Kondo hybridization and a relocalization of U 5f moments with an antiferromagnetic coupling. The preservation of universal scaling at a different muon site demonstrates a coexistence of itinerant and localized 5f electron states preceding the superconducting phase transition.

The subtle interplay between competing degrees of freedom, crystal electric fields, and spin correlations can lead to exotic quantum states in 4f ion-based frustrated triangular lattice antiferromagnets. We present the crystal structure, thermodynamic and muon spin relaxation (μSR) studies of the 4f ion-based frustrated magnet Ba4YbReWO12, wherein Yb3+ ions constitute a triangular lattice. The magnetic susceptibility does not show any signature of spin freezing down to 1.9 K or long-range magnetic ordering down to 0.4 K. The low-temperature Curie-Weiss fit to the inverse magnetic susceptibility data reveals a weak antiferromagnetic exchange interaction, which is corroborated by the fit of magnetic specific heat data following the J1-J2 model with the nearest neighbor exchange interaction of J1 = -0.197 K between the Jeff = 1/2 states of the Yb3+ moments in the lowest Kramers doublet. The lowest Kramers ground state doublet is well separated from the first excited state with a gap of 278 K, as evidenced by our μSR experiments that support the realization of Jeff = 1/2 at low temperatures. The specific heat experiments do not detect a phase transition down to 56 mK. The magnetic specific heat shows a broad maximum 90 mK suggesting a disordered ground state with short range spin correlations. The associated magnetic entropy release at low temperatures is consistent with that expected for the Jeff = 1/2 state. The zero-field μSR measurements show neither the signature of spin freezing nor a phase transition, at least down to 43 mK. Our results suggest a dynamic, disordered ground state in this Jeff = 1/2 frustrated triangular lattice antiferromagnet. Ba4RReWO12 (R=rare earth) offers a viable platform to realize intriguing quantum states borne out of spin-orbit coupling and frustration

We investigate magnetic properties of the s = 1/2 compound K2Cu3(MoO4)(4) by combining magnetic susceptibility, magnetization, specific heat, and electron spin resonance (ESR) with density functional calculations. Its monoclinic structure features alternating Cu2+ (s = 1/2) monomers and edge-shared dimers linked by MoO4 units, forming a distorted diamond chain along the a axis. Antiferromagnetic order occurs at T-N = 2.3 K, as evident from a lambda-type anomaly in specific heat and magnetic susceptibility derivatives. Inverse magnetic susceptibility reveals coexisting ferro-and antiferromagnetic interactions. Specific heat and ESR data show two characteristic temperatures: one at 20 K, associated with spin-singlet formation in Cu2O9 dimers, and another at 3.68 K, indicating short-range correlations between dimers and monomers. Magnetization measurements reveal a metamagnetic transition at 2.6 T and a critical magnetic field mu H-0(c) = 3.4 T, where a 1/3 magnetization plateau emerges with saturation near 0.35 mu (B). Low-temperature specific heat and magnetization data reveal the suppression of long-range order at mu H-0(c), enabling the construction of a temperature-magnetic field phase diagram showing multiple magnetic phases near the mu H-0(c). Density functional theory confirms a distorted diamond chain with J J1 dimers and competing J(2), J(4), J(3), and J(5) interactions with monomer spins as an effective low-temperature spin model.

We present a comprehensive muon spin relaxation/rotation (mu SR) study of the Co2+-based alternating Heisenberg Jeff = 12 spin chain system Sr2Co(SeO3)3. Low-temperature magnetic property measurements confirm a spin-singlet ground state and identify two critical fields, HC1 and HC2. At HC1, the system evolves from the spin-singlet state to a canted antiferromagnetic phase, which persists up to HC2, where the system enters a fully polarized state. This magnetically ordered phase exists between mu 0HC1 perpendicular to c = 2 T and mu 0HC2 perpendicular to c= 3.05 T for mu 0H perpendicular to c and between mu 0H//cC1= 2 T and mu 0H//c C2 = 3.6 T for H /c, reflecting the presence of anisotropy. Additionally, mu SR results provide insights into the thermal and field evolution of spin dynamics, revealing a thermal crossover in spin correlations, the reopening of a spin gap due to anisotropy above HC1, and the emergence of a magnon gap above HC2. These findings imply the suppressed criticality of the canted antiferromagnetic phase by anisotropy. Our study establishes Sr2Co(SeO3)3 as a model system for investigating field-driven quantum phase transitions in one-dimensional Jeff = 12 quantum spin chains with anisotropy.

We examined the electronic structures and optical properties of single crystals of RCd3P3 (R = Ce or La). Our first-principles analysis indicates that CeCd3P3 and LaCd3P3 exhibit semiconductor characteristics with narrow energy gaps of ~0.51 and 0.70 eV, respectively. Notably, a slight displacement of the Cd and P atoms within the unit cell significantly transforms the electronic structure from insulating to metallic state. Optical spectroscopy of both compounds reveals a metallic state with a low charge carrier density, suggesting a finite density of states at the Fermi level. A comparison between the theoretical electronic structures and experimental optical properties elucidates the observed metallic behavior. Additionally, the notable modification of the infrared-active phonons strongly indicates a structural phase transition in these compounds. Our findings also suggest that CeCd3P3 serves as a suitable platform for investigating the photoinduced Kondo effect due to its metallic ground state with limited charge carriers. This study explores the unique properties of certain materials called RCd3P3 compounds, which have a special arrangement of atoms that can lead to interesting electronic behaviors. Researchers used a combination of experiments and theoretical calculations to investigate these compounds. They grew single crystals of the materials and measured their optical properties at various temperatures. They also performed detailed calculations to predict how the atoms in the material might move and affect its electronic properties. The key finding is that small changes in the positions of certain atoms (Cd1 and P1) can cause the material to switch between acting like a metal and a semiconductor. This behavior is linked to a structural phase transition, where the arrangement of atoms changes slightly. Researchers conclude that understanding these transitions could help in designing new materials with specific electronic properties. This summary was initially drafted using artificial intelligence, then revised and fact-checked by the author. Broadband optical spectroscopy is used to obtain optical spectra of RCd₃P₃ (R: Ce or La), which exhibit a Fermi-liquid behavior with a very low charge carrier density. Notably, our first-principles calculations suggest that subtle displacements of Cd1 and P1 atoms within the unit cell can induce a semiconductor-to-metal transition, emphasizing the sensitivity of electronic structures to atomic positioning. The temperature-dependent anomalies of infrared-active phonons suggest a structural phase transition in these compounds. Our findings will offer a fundamental understanding of structural distortions leading to electronic transitions, which may be relevant for broader applications in correlated electron systems.

The recent discovery of a Kondo condensate in phosphorus‐doped silicon (Si:P) presents its significant potential for achieving novel many‐body quantum states. Si:P exhibits Kondo condensation, characterized by an energy gap in the electronic density of states, while the precise nature of its magnetic state has yet to be determined. Here, we utilize electron and muon spin resonance (ESR and µ SR) techniques, optical spectroscopy, and specific heat measurements to unravel the magnetic ground state and spin dynamics of Si:P. Both optical and ESR spectroscopy reveal the onset of spin correlations below 150 K. Furthermore, the muon spin relaxation rate exhibits a power‐law increase, λ ZF ∼ T −0.26(5) , below T KC ≈ 0.2 K, indicating the emergence of critical spin fluctuations within the Kondo condensate state. Strikingly, the concomitant occurrence of a Bardeen‐Cooper‐Schrieffer‐like charge gap and power‐law magnetic fluctuations closely parallels the pseudogap phases observed in doped Mott insulators. These findings evince that the critical spin fluctuations of the Kondo condensate state act as a driving force for pseudogap formation within inhomogeneous Kondo clouds.

The effect of pressure on the low-temperature states of the Re3Ge7 is investigated by both electrical and Hall resistance and magnetization measurements. At ambient pressure, the temperature-dependent resistance of Re3Ge7 behaves quasilinearly from room temperature down to 60 K, then undergoes a two-step metal-toinsulator transition (MIT) at temperatures T1 = 59.4 K and T2 = 58.7 K, which may be related to a structural phase transition or occurrence of charge-density wave ordering. Upon applying pressure, the two-step (T1, T2) MIT splits into three steps (T1, T2. and T3) above 1 GPa, and all traces of MITs are fully suppressed by -8 GPa. Subsequently, the onset of bulk superconductivity (SC) occurs between 10.8 and 12.2 GPa and persists to our highest pressure of 26.8 GPa. At 12.2 GPa the superconducting transition temperature, Tc, and upper critical field, Hc2 reach the maximum of Tc (onset) -5.9 K and Hc2 (1.8 K) -14 kOe. Our results not only present the observation of SC under high pressure in Re3Ge7 but also delineate the interplay between SC and other competing electronic states by creating a T-p phase diagram for this potentially topologically nontrivial system Re3Ge7.

Three novel alkali metal vanadium(III) fluoride sulfates, A(2)VF(3)(SO4) (A = K, Rb, Cs), were prepared through hydrothermal redox reactions. The products were isostructural with previously reported K2MnF3(SeO4) and featured one-dimensional chains of trans-VF4O2 octahedra that were connected by mu 2-bridging oxygen atoms with SO4 units. In the title compounds, spin chains of V3+ (S = 1) with trans V-F-V bridges were arranged in a two-dimensional rectangular lattice. DC magnetization showed unpredictable ferromagnetic-like ordering at similar to 0.6 K, accompanied by a weak hysteresis curve. At high temperatures, the dominant magnetic interactions were found to be antiferromagnetic, as deduced from the negative values of the Curie-Weiss temperature.

We report thermodynamic and transport properties of LaCuxSb2 (0.92 x 1.12), synthesized by controlling the initial loading composition and investigated by magnetization, electrical resistivity, and specific heat measurements. The physical properties of this system are highly dependent on Cu-site occupancy x, where residual resistivity ratio (RRR), magnetoresistance (MR), superconducting transition temperature (Tc), and electronic specific heat coefficient (gamma ) indicate a systematic variation as a function of x. The Shubnikov-de Haas quantum oscillations are observed in magnetoresistance measurements for samples close to the Cu stoichiometry x <^> 1, while the de Haas-van Alphen oscillations are detected in a wide range of x (0.92 x 1.12). For H H c, the oscillation frequency indicates a clear x-dependence, implying a systematic change of Fermi surface. DFT calculations for the sample closest to ideal Cu stoichiometry reveal electronic structures with a common feature of the square-net-based semimetals, which is in good agreement with the experimental observations. The magnetic response of LaCuxSb2 to magnetic fields is anisotropic owing to the Fermi surface anisotropy. Our results show how the physical properties are influenced by the Cu-site occupancy x, linked to the electronic bands arising from the Sb square net.

YbCdCu4 has been characterized as a heavy-fermion Kondo lattice system without long-range magnetic order. Thermodynamic and transport data of this compound have been partially analyzed, and the reported Kondo temperatures T-K are highly dependent on samples and estimation methods. In particular, the magnetic susceptibility chi(T) of this compound does not show the maximum corresponding to the Kondo resonance with a large degeneracy of the ground state, partly due to the sample quality. Thus, single crystals of YbCdCu4 are grown to reinvestigate their physical properties by means of magnetization, specific heat, electrical resistivity, Hall resistivity, and thermoelectric power measurements. Unlike earlier studies, we found consistencies regarding the T-K similar to 160 K measurement estimated from thermodynamic and transport property measurements. The magnetic part of the specific heat C-m displays a broad maximum near 70 K, which follows well with the prediction made by the Coqblin-Schrieffer (C-S) model for whole J = 7/2 multiplets involved in the formation of the Kondo state. However, the local maximum in chi(T) does not match well with the C-S model prediction due to the crystalline electric field (CEF) effect, where the T-K value is still greater than the overall CEF splittings: T-K > Delta(CEF). Electrical resistivity and Hall coefficient measurements indicate an extremum near similar to 70 K, while a negative minimum at similar to 130 K is observed in thermoelectric power.

High -entropy alloys (HEAs) are novel functional materials that exhibit excellent mechanical and chemical properties. Recent discovery of self -healing superconductivity of HEAs under ion irradiation suggests their great potential applications under extreme conditions such as in nuclear fusion reactors or space environments. Here, we report a fabrication of the HEA superconducting (SC) wires using the ex -situ powder -in -tube (PIT) technique for the first time, a crucial stepping stone to achieve various industrial and technological applications. The Ta 1/ 6 Nb 2/6 Hf 1/6 Zr 1/6 Ti 1/6 HEA SC powder prepared by planetary ball milling was filled into Fe tubes, drawn into wires, and then sintered in evacuated quartz tubes at various temperatures. The HEA SC wire sintered at 700 degrees C for 1 h exhibits the highest critical current density ( J c ) among the HEA SC wires sintered in the temperature range of 600 - 1000 degrees C. At 4.2 K, the J c of this wire exceeds the common benchmark value of J c = 100 kA cm -2 , indicating the suitability of the HEA wire for large-scale applications, such as in high -field SC magnets. The SC transition temperature ( T c ) of the HEA wire significantly increases from 5.10 K for the as -cast wire to 7.58 K with the sintering time ( t s ) of 30 min at 700 degrees C. The scaling of the flux pinning force as a function of the magnetic field indicates that normal point pinning plays a major role in achieving a high in -field J c in HEA SC wires. These results underscore the significant potential of HEA superconductors for practical applications in high -field SC magnets, SC electric machines, and next -generation nuclear fusion reactors.

CeCd$_3$P$_3$ and CeCd$_3$As$_3$ compounds adopt the hexagonal ScAl$_3$C$_3$-type structure, where magnetic Ce ions on a triangular lattice order antiferromagnetically below $T_\text{N} \sim$0.42~K. Their crystalline electric field (CEF) level scheme has been determined by fitting magnetic susceptibility curves, magnetization isotherms, and Schottky anomalies in specific heat. The calculated results, incorporating the CEF excitation, Zeeman splitting, and molecular field, are in good agreement with the experimental data. The CEF model, with Ce$^{3+}$ ions in a trigonal symmetry, explains the strong easy-plane magnetic anisotropy that has been observed in this family of materials. A detailed examination of the CEF parameters suggests that the fourth order CEF parameter $B_{4}^{3}$ is responsible for the strong CEF induced magnetocrystalline anisotropy, with a large $ab$-plane moment and a small $c$-axis moment. The reliability of our CEF analysis is assessed by comparing the current study with earlier reports of CeCd$_{3}$As$_{3}$. For both CeCd$_{3}X_{3}$ ($X$ = P and As) compounds, less than 40 \% of $R\ln(2)$ magnetic entropy is recovered by $T_\text{N}$ and full $R\ln(2)$ entropy is achieved at the Weiss temperature $\theta_{p}$. Although the observed magnetic entropy is reminiscent of delocalized 4$f$-electron magnetism with significant Kondo screening, the electrical resistivity of these compounds follows a typical metallic behavior. Measurements of thermoelectric power further validate the absence of Kondo contribution in CeCd$_{3}X_{3}$.

The electrical resistivity of GdCuAs2 single crystals exhibits an anomalous Kondo-like resistivity minimum above the antiferromagnetic ordering temperature TN1 approximate to 10.6 K, which is unusual for a highly localized 4f-moment (Gd3+) system. Using x-ray resonant magnetic scattering, we determined the magnetic structure of GdCuAs2, where Gd moments are antiferromagnetically aligned along the crystallographic a axis and in the (+ + --) arrangement in the c direction and ferromagnetically arranged in the b direction. The antiferromagnetic order appears first at q = (delta, 0, 0.5) below 10 K, with an incommensurate modulation along the a axis and locks into a commensurate position at q = (1/3, 0, 0.5) below TN2 approximate to 6 K. Our high-resolution x-ray diffraction measurements show a two-peak structure at Q = (2, 0, 6) above the resistivity minimum, suggesting a lower-symmetry crystal structure than the reported tetragonal structure, and the Q = (2, 0, 6) peak becomes a sharp one-peak structure below the resistivity minimum, implying a magnetoelastic coupling above TN. Our findings suggest a complex interplay between the crystal structure and antiferromagnetic structure through a magnetoelastic coupling, associated with the anomalous resistivity minimum above TN1 .

Single crystals of RNi4Cd (R = Ce, Nd, Sm, and Gd - Tm) are grown by Cd flux and their physical properties are investigated by means of x-ray diffraction, magnetization, electrical resistivity, and specific heat measurements. Except for R = Ce, the unit cell volume of RNi4Cd follows a lanthanide contraction, implying a 3+ valence state of rare-earth ions in this series. At high temperatures, magnetic susceptibility curves for R = Nd and Gd-Tm follow the Curie-Weiss behavior. The obtained Curie-Weiss temperature (Op) for R = Gd-Tm is small and negative. The temperature dependence of the electrical resistivity shows a metallic behavior for all RNi4Cd compounds. Of the thermodynamic and transport property measurements, only GdNi4Cd indicates an antiferromagnetic ordering below TN = 4.5 K, while the remaining compounds show no signature of magnetic transition down to 1.8 K. The Ruderman-Kittel-Kasuya-Yosida (RKKY) exchange mechanism is examined for its relevance to TN and Op of isostructural metallic RT4X (R = Gd-Tm, T = Cu and Ni, and X = Cd, In, Mg, Pd, Ag, and Au) compounds. Although the variation in Op can be qualitatively explained by the RKKY sum, the values of Op in this family are highly dependent on their lattice parameter. Unlike the RCu4X, the strength of the exchange interaction between molecular fields produced by rare-earth planes is strongly suppressed by the lattice contraction in RNi4X compounds.