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We present thermopower measurements on Yb( Rh 1 - x Co x ) 2 Si 2 . Upon cobalt substitution, the Kondo temperature is decreasing and the single large thermopower minimum observed for YbRh 2 Si 2 splits into two minima. Simultaneously, the absolute thermopower values are strongly reduced due to a weaker exchange coupling between the 4f and the conduction electron states with increasing x. Pure YbCo 2 Si 2 is considered a stable trivalent system. Nevertheless, we still observe two minima in the thermopower indicative of weak residual Kondo scattering. This is in line with results from photoemission spectroscopy revealing a tiny contribution from Yb 2 + . The value at the high-T minimum in S(T) is found to be proportional to the Sommerfeld coefficient for the whole series. This unexpected finding is discussed in relation to recent measurements of the valence and Fermi surface evolution with temperature. [ABSTRACT FROM AUTHOR]

The crystal electric field (CEF) scheme of YbNi4P2 is determined, based on experimental data from inelastic neutron scattering, heat capacity, susceptibility andNMRmeasurements. Despite the tetragonal crystal structure, 9 parameters are needed to describe the crystal field in YbNi4P2 due to the orthorhombic site symmetry of the Yb ion. Alarge basal plane anisotropy is detected by the local probe NMR. Our analysis yields CEF excitation energies of 8.5, 12.5 and roughly 30 meV and a ground state wave function that is dominated by the 5 2 state. Furthermore, we present an analysis of the CEF scheme based on density functional theory calculations, which confirms the large basal plane anisotropy. [ABSTRACT FROM AUTHOR]

The Kondo model predicts that both the valence at low temperatures and its temperature dependence scale with the characteristic energy TK of the Kondo interaction. Here, we study the evolution of the 4f occupancy with temperature in a series of Yb Kondo lattices using resonant X-ray emission spectroscopy. In agreement with simple theoretical models, we observe a scaling between the valence at low temperature and TK obtained from thermodynamic measurements. In contrast, the temperature scale Tv at which the valence increases with temperature is almost the same in all investigated materials while the Kondo temperatures differ by almost four orders of magnitude. This observation is in remarkable contradiction to both naive expectation and precise theoretical predictions of the Kondo model, asking for further theoretical work in order to explain our findings. Our data exclude the presence of a quantum critical valence transition in YbRh2Si2. [ABSTRACT FROM AUTHOR]

We have investigated single crystals of two substitution series Ce(Ru1−x Fex)PO and CeFe(As1−y Py)O in the vicinity to the quantum critical material CeFePO by means of magnetic-susceptibility and specific-heat measurements. We observe an antiferromagnetic ground state in the vicinity of the quantum critical point, with pronounced metamagnetic transitions for [ABSTRACT FROM AUTHOR]

Presents a study which analyzed the leading non-linear term of the susceptibility of the singlet-ground-state heavy-fermion superconductors UPd[sub2]Al[sub3]. Calculation of the crystal-electric-field (CEF) approach for singlet-ground-state systems; Correlations of magneto-elastic couplings; Measurement of the CEF level scheme.

Ferromagnetic correlations are discussed on the basis of shift K4 f and spin-lattice-relaxation (SLR) rate R4 f( T) = (1/ T1 T)4 f investigations for YbNi4P2 and YbRh2Si2. For YbRh2Si2 the coexistence of antiferromagnetic (afm) and ferromagnetic (fm) fluctuations at the edge of magnetic order is strongly related to the non-Fermi-liquid behaviour (NFL). The analysis of the NMR results for YbNi4P2 in the modified Korringa framework for correlated local moment metals yields the enhancement factor $\cal K$( α) which is a measure of the q -space dependence of the complex dynamic susceptibility. Surprisingly the $\cal K$( α) behavior of YbNi4P2is very similar to YbRh2Si2and evidences strongly the evolution of an afm ( q ≠ 0) component in the q = 0 dominated complex dynamic susceptibility χ'' ( q,ωn,T) at low temperatures and in small fields. This suggests the presence of ferro- and antiferromagnetic fluctuations at the QCP and the freezing out of the afm ones by applying magnetic fields and tuning towards FL state. (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

We present a new Kondo-lattice system, YbNi4P2, which is a clean heavy-fermion metal with a severely reduced ferromagnetic (FM) ordering temperature at TC = 0.17 K, evidenced by distinct anomalies in susceptibility, specific heat and resistivity measurements. The FM nature of the transition, with only a small ordered moment of ~0.05μB, is established by a diverging susceptibility at TC with huge absolute values in the ferromagnetically ordered state, severely reduced by small magnetic fields. Furthermore, YbNi4P2 is a stoichiometric system with a quasi-one-dimensional crystal and electronic structure and strong correlation effects which dominate the low-temperature properties. This is reflected by a stronger-than-logarithmically diverging Sommerfeld coefficient and a linear-in-T resistivity above TC, which cannot be explained by current theoretical predictions. These exciting characteristics are unique among all correlated electron systems and make this an interesting material for further in-depth investigations. [ABSTRACT FROM AUTHOR]

We report on a comprehensive study of the magnetic properties of YbCo2Si2 investigated using a single crystal. All data confirm a stable trivalent Yb state carrying a well-localized 4f moment, as well as a non-magnetic Co state. We observed a sizeable anisotropy in the magnetic susceptibility χ(T ), with the moment in the basal plane twice as large as that along the c-direction. Combining this result with published neutron-scattering data puts strong constraints on the values of the crystalline electrical field (CEF) parameters. Our calculation yields one possible solution with a Γ7 CEF ground state. A peak in the easy-plane susceptibility at low temperatures demonstrates that the previously reported magnetic ordering at TN ≈ 1.65K is of antiferromagnetic (AFM) nature. In addition, we observed sharp anomalies in all measured properties, evidencing a further phase transition at TL ≈ 0.9 K, found to be first order, which corresponds to a change in the AFM structure. Both transitions are suppressed by a magnetic field B = 2 T. Below TL the specific heat, C4f, shows a well-defined T 3 dependence, as expected for AFM spin-wave excitations. Surprisingly, the resistivity, ρ(T ), also shows a T 3 power law in the same temperature range, instead of the expected T 5. This discrepancy might be related to more complex magnetic interactions, as also evidenced by the multiple transitions. By extending the linear fit of C4f/T versus T ² to T = 0, the Sommerfeld coefficient γ0 = 0.13 JK-2 mol-1 is extracted. Although magnetism in YbCo2Si2 is dominated by the RKKY exchange interaction, the enhanced 0 and a weak Kondo-like increase in ρ(T ) indicate the presence of some interactions between the conduction electrons and the 4f moments. [ABSTRACT FROM AUTHOR]

The entanglement of quantum states is both a central concept in fundamental physics and a potential tool for realizing advanced materials and applications. The quantum superpositions underlying entanglement are at the heart of the intricate interplay of localized spin states and itinerant electronic states that gives rise to the Kondo effect in certain dilute magnetic alloys. In systems where the density of localized spin states is sufficiently high, they can no longer be treated as non-interacting; if they form a dense periodic array, a Kondo lattice may be established. Such a Kondo lattice gives rise to the emergence of charge carriers with enhanced effective masses, but the precise nature of the coherent Kondo state responsible for the generation of these heavy fermions remains highly debated. Here we use atomic-resolution tunnelling spectroscopy to investigate the low-energy excitations of a generic Kondo lattice system, YbRh2Si2. We find that the hybridization of the conduction electrons with the localized 4f electrons results in a decrease in the tunnelling conductance at the Fermi energy. In addition, we observe unambiguously the crystal-field excitations of the Yb3+ ions. A strongly temperature-dependent peak in the tunnelling conductance is attributed to the Fano resonance resulting from tunnelling into the coherent heavy-fermion states that emerge at low temperature. Taken together, these features reveal how quantum coherence develops in heavy 4f-electron Kondo lattices. Our results demonstrate the efficiency of real-space electronic structure imaging for the investigation of strong electronic correlations, specifically with respect to coherence phenomena, phase coexistence and quantum criticality. [ABSTRACT FROM AUTHOR]

The origin of unconventional superconductivity, including high-temperature and heavy-fermion superconductivity, is still a matter of controversy. Spin excitations instead of phonons are thought to be responsible for the formation of Cooper pairs. Using inelastic neutron scattering, we present the first in-depth study of the magnetic excitation spectrum in momentum and energy space in the superconducting and the normal states of CeCu2Si2. A clear spin excitation gap is observed in the superconducting state. We determine a lowering of the magnetic exchange energy in the superconducting state, in an amount considerably larger than the superconducting condensation energy. Our findings identify the antiferromagnetic excitations as the main driving force for superconducting pairing in this prototypical heavy-fermion compound located near an antiferromagnetic quantum critical point. [ABSTRACT FROM AUTHOR]

any pressure sensitive quantum critical point (QCP) the thermal expansion is more singular than the specific heat leading to a divergence of the Grüneisen parameter. For a magnetic field sensitive QCP, the complementary property is the magnetic Grüneisen ratio which equals the magnetocaloric effect. Here we use both properties to investigate magnetic QCPs in different heavy fermion (HF) metals starting from CeNiGe. The influence of dimensionality on quantum criticality is addressed by the comparison of cubic CeInSn with layered CeMInSn (M = Co, Rh) systems, in which Sn doping both acts as tuning parameter and introduces slight disorder. Near the field-tuned QCP in undoped CeCoIn a crossover scale T is discovered which separates 2D (at T> T) from 3D (at T< T) quantum criticality. Disorder, introduced by Sn-doping, is found to increase T, stabilizing 3D behavior. We also compare the magnetic Grüneisen ratio in the approach of the field-tuned QCP in YbRhSi with zero-field Grüneisen parameter data on YbRh(SiGe) ( x=0, x=0.05). Both properties indicate quantum criticality incompatible with the predictions of the itinerant theory. [ABSTRACT FROM AUTHOR]

The unconventional nature of the quantum criticality in YbRhSi is highlighted on the basis of magnetoresistivity and susceptibility measurements. Results obtained under chemical pressure realized by isoelectronic substitution on the rhodium site are presented. These results illustrate the position of the T-line associated with a breakdown of the Kondo effect near the antiferromagnetic instability in the low-temperature phase diagram. Whereas at zero temperature the Kondo breakdown and the antiferromagnetic quantum critical point coincide in the proximity of the stoichiometric compound, they are seen to be detached under chemical pressure: For positive chemical pressure the magnetically ordered phase extends beyond the T( B)-line. For sufficiently high negative pressure the T( B)-line is separated from the magnetically ordered phase. From our detailed analysis we infer that the coincidence is retained at small iridium concentrations, i.e., at small negative chemical pressure. We outline further measurements which may help to clarify the detailed behavior of the two instabilities. [ABSTRACT FROM AUTHOR]

Phase separation and extreme sensitivity to disorder and defects are key features of electronic order near quantum phase transitions. Neutron depolarization imaging and neutron Larmor diffraction are new experimental techniques capable of providing detailed real-space and reciprocal-space information, respectively, on the existence and nature of phase separations. Proof-of-principle depolarization imaging in PdNi, CePdRh and NbFe suggests distinct differences of the real-space distribution of ferromagnetic moments and Curie temperatures in materials at ferromagnetic quantum phase transitions. This compares with neutron Larmor diffraction which provides high-resolution reciprocal-space information of phase separation and the absence of quantum criticality in the itinerant helimagnet MnSi or the parasitic nature of small moment antiferromagnetism in URuSi. [ABSTRACT FROM AUTHOR]

We have investigated the pressure dependence of the magnetic field-temperature phase-diagram of the tetragonal compound YbRu2Ge2 by electrical resistivity measurements in the pressure range up to 10 GPa and for magnetic fields up to 14 T. [ABSTRACT FROM AUTHOR]

We develop a theoretical basis for understanding the spin relaxation processes in Kondo lattice systems with heavy fermions as experimentally observed by electron spin resonance (ESR). The Kondo effect leads to a common energy scale that regulates a logarithmic divergence of different spin kinetic coefficients and supports a collective spin motion of the Kondo ions with conduction electrons. We find that the relaxation rate of a collective spin mode is greatly reduced due to a mutual cancellation of all the divergent contributions even in the case of the strongly anisotropic Kondo interaction. The contribution to the ESR linewidth caused by the local magnetic field distribution is subject to motional narrowing supported by ferromagnetic correlations. The developed theoretical model successfully explains the ESR data of YbRh2Si2 in terms of their dependence on temperature and magnetic field. [ABSTRACT FROM AUTHOR]

A continuous phase transition driven to zero temperature by a non-thermal parameter, such as pressure, terminates in a quantum critical point (QCP). At present, two main theoretical approaches are available for antiferromagnetic QCPs in heavy-fermion systems. The conventional one is the quantum generalization of finite-temperature phase transitions, which reproduces the physical properties in many cases. More recent unconventional models incorporate a breakdown of the Kondo effect, giving rise to a Fermi-surface reconstruction— YbRh2Si2 is a prototype of this category. In YbRh2Si2, the antiferromagnetic transition temperature merges with the Kondo breakdown at the QCP. Here, we study the evolution of the quantum criticality in YbRh2Si2 under chemical pressure. Surprisingly, for positive pressure we find the signature of the Kondo breakdown within the magnetically ordered phase, whereas negative pressure induces their separation, leaving an intermediate spin-liquid-type ground state over an extended range. This behaviour suggests a new quantum phase arising from the interplay of the Kondo breakdown and the antiferromagnetic QCP. [ABSTRACT FROM AUTHOR]

PrRh2Si2 is highly anisotropic Ising-type antiferromagnetic system. The ordering temperature ( T N~ 68 K) of PrRh2Si2 is exceptionally high on the de-Gennes scale in the family of RRh2Si2 (R = rare earths). The reason for this anomalous behaviour is not clear. It is believed that the presence of uniaxial anisotropy assists in enhancing the T N. The Mössbauer study was performed on a 10% Fe-doped PrRh2Si2 sample to understand the magnetic coupling between different sites of PrRh2Si2. The Mössbauer spectra together with the magnetic susceptibility data suggest that the magnetic coupling in PrRh2Si2 is provided mainly by the RKKY interaction between Pr-moments. [ABSTRACT FROM AUTHOR]

Abstract: At any pressure-sensitive quantum critical point (QCP), the volume thermal expansion coefficient is more singular than the specific heat. Consequently, the resulting critical Grüneisen ratio Γ cr∼β cr/C cr, where β cr and C cr denote the thermal expansion and specific heat after subtraction of non-critical background contributions, diverges. The related critical exponent ε in Γ cr∼T −ε can be used to characterize the nature of the underlying quantum critical fluctuations. We have performed a comparative study on various heavy fermion (HF) systems close to antiferromagnetic QCPs. In particular, we have studied (i) CeIn3− x Sn x , (ii) CeNi2Ge2, (iii) YbRh2(Si0.95Ge0.05)2, as well as (iv) CeCu5.8Ag0.2, all of which show a divergent Grüneisen ratio. For the two former systems the critical exponent ε=1 is compatible with the predictions of the well-established Hertz–Millis–Moriya theory for three-dimensional extended quantum critical fluctuations. By contrast, for the two latter systems ε<1 is found to be incompatible with “conventional” quantum criticality. Our results thus suggest the existence of at least two different classes of QCPs in HF systems. [Copyright &y& Elsevier]

Abstract: We report on inelastic neutron scattering experiments on powder to study the low-energy spin dynamics at temperatures between and 22K. The low-energy magnetic response is quasielastic. However, it exhibits an unusual form not modelled by a simple relaxation rate yielding a Lorentzian lineshape, but can satisfactorily be described by a phenomenological model involving a distribution of relaxation rates. The lower bound of the relaxation rates varies roughly linear with temperature indicating a pronounced slowing down of the critical modes above the antiferromagnetic ordering temperature . [Copyright &y& Elsevier]

We have examined the magnetic properties of the heavy electron compounds YbAgGe and YbPtIn by 170Yb Mössbauer spectroscopy down to 0.1 K, and the crystal field properties of YbAgGe by Perturbed Angular Correlations (PAC) measurements up to 900 K. In YbAgGe, we show that each of the two magnetically ordered phases below 0.8 K involves a specific incommensurate modulation of the Yb moment. An analysis of existing low temperature specific heat data suggests the persistence of fluctuations of the correlated Yb spins down to 0.1 K. The PAC data allow to discriminate among proposed Yb3+ crystal field level schemes. In YbPtIn, we show that the low temperature magnetic order phase has an antiferro-para structure, where zero moment Yb ions coexist with large moment ones, and that a 90° moment reorientation occurs at 1.4 K. [ABSTRACT FROM AUTHOR]

A quantum critical point (QCP) develops in a material at absolute zero when a new form of order smoothly emerges in its ground state. QCPs are of great current interest because of their singular ability to influence the finite temperature properties of materials. Recently, heavy-fermion metals have played a key role in the study of antiferromagnetic QCPs. To accommodate the heavy electrons, the Fermi surface of the heavy-fermion paramagnet is larger than that of an antiferromagnet. An important unsolved question is whether the Fermi surface transformation at the QCP develops gradually, as expected if the magnetism is of spin-density-wave (SDW) type, or suddenly, as expected if the heavy electrons are abruptly localized by magnetism. Here we report measurements of the low-temperature Hall coefficient (RH)-a measure of the Fermi surface volume-in the heavy-fermion metal YbRh2Si2 upon field-tuning it from an antiferromagnetic to a paramagnetic state. RH undergoes an increasingly rapid change near the QCP as the temperature is lowered, extrapolating to a sudden jump in the zero temperature limit. We interpret these results in terms of a collapse of the large Fermi surface and of the heavy-fermion state itself precisely at the QCP. [ABSTRACT FROM AUTHOR]

In this paper we report a comprehensive study of the magnetic susceptibility (), resistivity (), and specific heat (), down to 0.5 K of the cubic CeIn3-xSnx alloy. The ground state of this system evolves from antiferromagnetic (AF) in CeIn3 (K) to intermediate-valent in CeSn3, and represents the first example of a Ce-lattice cubic non-Fermi liquid (NFL) system wherecan be traced down toT= 0 over more than a decade of temperature. Our results indicate that the disappearance of the AF state occurs near, although already atsignificant modifications of the magnetic ground state are observed. Between these concentrations, clear NFL signatures are observed, such as(withn<1.5) anddependencies. Within the ordered phase a first order phase transition occurs for 0.25

We discuss a series of thermodynamic, magnetic, and electrical transport experiments on the two heavy fermion compounds CeNi[sub2] Ge[sub2] and YbRh[sub2] Si[sub2] in which magnetic fields, B, are used to tune the systems from a non-Fermi liquid (NFL) into a field-induced FL state. Upon approaching the quantum- critical points from the FL side by reducing B we analyze the heavy quasi-particle (QF) mass and QP-QP scattering cross sections. For CeNi[sub2] Ge[sub2] the observed behavior agrees well with the predictions of the spin-density wave (SDW) scenario for three-dimensional (3D) critical spin-fluctuations. By contrast, the observed singularity in YbRh[sub2] Si[sub2] cannot be explained by the itinerant SDW theory for neither 3D nor 2D critical spinfluctuations. Furthermore, we investigate the magnetization M(B) at high magnetic fields. For CeNi[sub2] Ge[sub2] a metamagnetic transition is observed at 43 T, whereas for YbRh[sub2] Si[sub2] a kink-like anomaly occurs at 10 T in M vs B (applied along the easy basal plane) above which the heavy fermion state is completely suppressed. [ABSTRACT FROM AUTHOR]

The point at absolute zero where matter becomes unstable to new forms of order is called a quantum critical point (QCP). The quantum fluctuations between order and disorder[SUP1-5] that develop at this point induce profound transformations in the finite temperature electronic properties of the material. Magnetic fields are ideal for tuning a material as close as possible to a QCP, where the most intense effects of criticality can be studied. A previous study[SUP6] on the heavy-electron material YbRh[SUB2]Si[SUB2] found that near a field-induced QCP electrons move ever more slowly and scatter off one another with ever increasing probability, as indicated by a divergence to infinity of the electron effective mass and scattering cross-section. But these studies could not shed light on whether these properties were an artefact of the applied field[SUP7,8], or a more general feature of field-free QCPs. Here we report that, when germanium-doped YbRh[SUB2]Si[SUB2] is tuned away from a chemically induced QCP by magnetic fields, there is a universal behaviour in the temperature dependence of the specific heat and resistivity: the characteristic kinetic energy of electrons is directly proportional to the strength of the applied field. We infer that all ballistic motion of electrons vanishes at a QCP, forming a new class of conductor in which individual electrons decay into collective current-carrying motions of the electron fluid. [ABSTRACT FROM AUTHOR]

(The EPR signal from localized ytterbium ions was observed in an undoped YbRh)2(Si)2 compound with heavy fermions in the temperature range from 1.5 to 25 K. The exponential contribution dominating the temperature dependence of EPR line width at temperatures above 15 K was shown to be caused by the random transitions from the ground to the first excited Stark sublevel of the Yb(3+)(4f (13)) ion with the activation energyD = 115 K. [ABSTRACT FROM AUTHOR]

We present electrical resistivity and specific heat measurements of alloys on the Rh rich side of the phase diagram of the Ce(Rh1-xPdx)2Si2 system. We compare these results with those obtained at intermediate and low Rh concentrations. The analysis of the concentration and temperature dependence of the entropy and of the scaling behaviour of C el ( T ) and ρ( T ) clearly confirm a separation of the magnetic phase diagram into two regions: the region x ≤0.3, showing a concentration independent characteristic temperature for the 4 f-electrons with T 0 ≈ 45 K, while for x > 0.3, T0 decreases to T 0 ( x = 1) ≈ 15 K. At low Pd-content, TN decreases very rapidly from T N = 36 K in pure CeRh2Si2 to T N = 18 K at x = 0.1. With higher Pd concentration TN stabilizes at T N ≈ 15 K whereas the magnitude of the anomalies in C el ( T ) and in the susceptibility around TN are further reduced and disappear at x ≈ 0.3. This differs from the behavior found on the Pd-rich side, where TN decreases continuously to zero with increasing Rh content. The pronounced differences observed between both phase boundaries and the drastic effect of doping on the Rh rich side suggest an itinerant character in CeRh2 Si2, in contrast with the localized character of CePd2Si2. Further evidence for the itinerant character of CeRh2Si2 is given by the ρ( T ) dependence observed for x ≤0.3, which scales with ρ( T ) of the prototype itinerant compound YCo2. [ABSTRACT FROM AUTHOR]

Temperature-dependent electron paramagnetic resonance (EPR) studies were performed on CuSiO3. This recently discovered compound is isostructural with the spin-Peierls compound CuGeO3. The EPR signals show characteristics different from those of CuGeO3 and are due to Cu2+ spins located along quasi one-dimensional chains. For T>8.2 K the spin susceptibility closely follows the predictions of an S=1/2 one-dimensional Heisenberg antiferromagnet with J/k B=21 K. Below T=8.2 K the spin susceptibility immediately drops to zero indicating long-range magnetic order. [ABSTRACT FROM AUTHOR]

The antiferromagnetic (AFM) state is investigated in the three heavy-fermion compounds URu[sub 2]Si[sub 2], UPd[sub 2]Al[sub 3], and UNi[sub 2]Al[sub 3] by measuring dV/dI(V) curves of point contacts at different temperatures 1.5-20 K and magnetic fields 0-28 T. The zero-bias maximum in dV/dI(V) for URu[sub 2]Si[sub 2] points to a partially gapped Fermi surface related to the itinerant nature of the AFM state, contrary to the case of UPd[sub 2]Al[sub 3], where analogous features have not been found. The AFM state in UNi[sub 2]Al[sub 3] has more similarities with URu[sub 2]Si[sub 2]. For URu[sub 2]Si[sub 2], the same critical field of about 40 T along the easy axis c is found for all features in dV/dI(V), corresponding to the Néel temperature, the gap in the electronic density of states, and presumably the ordered moments. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Reports the detection of a dispersive excitation of the ordered f-electron moments, which shows a strong interaction with the heavy superconducting electrons. How the magnetic exciton moves through the lattice as a result of exchange forces between the magnetic moments; Argument that these magnetic excitons can produce effective interactions between the itinerant electrons and be responsible for superconductivity in a manner analogous to the role played by phonons in conventional superconductors.

We report Cu-NQR results on Ge-doped heavy-fermion superconductor CeCu2(Si1− xGe x)2 (0< x≤0.2) and undoped Ce0.99Cu2.02Si2. The main effect of the Ge doping is considered to be a negative pressure, since the strength of hybridization decreases by the Ge doping. With increasing x, the dynamical characteristics of the magnetic order at x=0 change to more static ones which suggests a localized regime above x∼0.25. From the derived T– x phase diagram, it is suggested that the magnetic and the superconducting phases are almost degenerate in undoped CeCu2Si2. An exotic interplay between the magnetism characterized by the slow fluctuations and the superconductivity is implied in the region of small x. [ABSTRACT FROM AUTHOR]

We report muon spin relaxation (μ+SR) studies on the magnetic phase diagram of Ce(Cu1-xNix)2Ge2 polycrystals for 0.5≤ x ≤ 0.8. A sharp magnetic transition, evidenced by the appearance of a fast Gaussian relaxation component σ, has been observed in the x = 0.5 alloy at 4.0 K in zero applied field. The average local field < Bμ> at the stopping sites of the muons, extracted from σ, exhibits a linear temperature dependence. We associate these features with an incommensurate spin density wave (SDW) ordering. Magnetic ordering, either long range or short range, and signatures of non-Fermi liquid behaviour have not been observed down to 2.0 K at x = 0.8. [ABSTRACT FROM AUTHOR]