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The cerium-based compound $\mathrm{Ce}{\mathrm{Pt}}_{6}{\mathrm{Al}}_{3}$, in which Ce atoms form a honeycomb lattice hosting magnetic frustration, has a heavy-fermion ground state. We have observed development of magnetic order in partially Pd-substituted $\mathrm{Ce}{({\mathrm{Pt}}_{1\ensuremath{-}x}{\mathrm{Pd}}_{x})}_{6}{\mathrm{Al}}_{3}$ series up to $x$ = 0.3 by the measurements of magnetic susceptibility, electrical resistivity \ensuremath{\rho}, and specific heat $C$. In the whole range of $x$, the unit cell volume remains unchanged within 0.2%, and the effective magnetic moment stays at $2.4\phantom{\rule{0.16em}{0ex}}{\ensuremath{\mu}}_{B}/\mathrm{Ce}$. For $x$ = 0.05, both $C/T$ and $\ensuremath{\rho}(T)$ jump on cooling at ${T}_{m}=1.8\phantom{\rule{0.28em}{0ex}}\mathrm{K}$. With increasing $x$ to 0.2, ${T}_{m}$ increases to 3.8 K, where $C/T$ shows a pronounced \ensuremath{\lambda}-type anomaly. Application of magnetic fields suppresses ${T}_{m}$, which is indicative of an antiferromagnetic (AFM) ordered state. Thus, a long-range AFM order is induced by the substitution of isovalent Pd for Pt in $\mathrm{Ce}{\mathrm{Pt}}_{6}{\mathrm{Al}}_{3}$ without carrier doping and chemical pressure. We attribute the emergence of AFM order in $\mathrm{Ce}{({\mathrm{Pt}}_{1\ensuremath{-}x}{\mathrm{Pd}}_{x})}_{6}{\mathrm{Al}}_{3}$ to the randomness in the spin-orbit interaction in the Pt-Pd sublattice, which weakens both the coherent Kondo effect and magnetic frustration in the honeycomb Kondo lattice.

The Nd 2 Pt 2 In compound was investigated by means of electrical resistivity ρ ( T ) , heat capacity C p ( T ) , magnetic susceptibility χ ( T ) , magnetization M ( μ 0 H ) and magnetocaloric effect (MCE) measurements. The material orders ferromagnetically at T C = 16 K with a second - order phase transition. In the ordered state, ρ ( T ) can be represented in terms of ferromagnetic (FM) spin - wave dispersion with an energy gap Δ R = 13(1) K in zero field. In concert, the C p ( T ) data in this region can be well described by the same model getting Δ C = 8(1) K in zero field. Above T C , the ρ ( T ) variation is characteristic of electron - phonon interaction in the presence of s − d scattering and crystalline-electric field (CEF). The 4 f - electron specific heat shows a Schottky - type anomaly around 60 K associated with CEF. On the other hand, C p ( T ) data of the non-magnetic homologue La 2 Pt 2 In can be described by the Debye - Einstein model, giving a Debye and Einstein temperature values of 190.3(5) K and 69.8(7) K respectively. At high temperatures, the χ ( T ) data follows the Curie - Weiss relation with an effective magnetic moment μ e f f = 3.61(2) μ B and a Weiss temperature θ p = 17(1) K. The magnitude of MCE was estimated from the isothermal magnetization data to be 6.25 J/(kg.K), 5.01 J/(kg.K), 3.18 J/(kg.K) and 0.47 J/(kg.K) for a field change of 7 T, 5 T, 3 T and 1 T, respectively. The characteristic behaviour of the isothermal magnetic entropy change points to a second - order character of the FM phase transition.

PrCo$_2$Ga$_8$ is an orthorhombic quasi-skutterudite type compound which crystallizes in the CaCo$_2$Al$_8$ structure type, with space group $Pbam$ (No. 55). The Pr$^{3+}$ ion has a site symmetry of $C_s$ which predicts a crystal electric field (CEF) level splitting into 9 singlets for $J$ = 4. However, a phase transition at $T_m$ = 1.28~K is observed in electrical resistivity and specific heat results and is reported in this paper. The electrical resistivity shows an upturn below $T_m$ due to the superzone-gap formation. This transition is tuneable in fields and is suppressed to lower temperatures with applied magnetic fields. The electronic specific heat $C_{p}(T)/T$ increases below $T_m$ and reaches a value of 7.37 J/(mol K$^2$) at 0.4~K. The Sommerfeld coefficient, $\gamma$ extracted from the low temperature analysis of $C_\mathrm{4f}(T)/T$ is 637 mJ/(mol K$^2$) indicating a possible mass enhancement of the quasiparticles. The calculated entropy value of 3.05 J/(mol K) is recovered around $T_m$ exhibiting almost 53% of Rln2, where R is the universal gas constant. Magnetic susceptibility results obeys the Curie-Weiss law for data above 100 K with an estimated effective magnetic moment, $\mu_\mathrm{eff}$ = 3.37 $\mu_B$/Pr and Weiss temperature, $\theta_p$ = $-$124 K., Comment: 11 pages, 5 figures, SCES 2017 conference proceedings

We report on X-ray diffraction, electrical transport, heat capacity and magnetocaloric effect measurements of a polycrystalline sample of Pr 2 Pt 2 In . The compound forms in the tetragonal Mo 2 FeB 2 type structure and orders ferromagnetically at T C =9 K. In the ordered state, its thermodynamic and electrical transport properties are dominated by magnon contributions with an energy gap of about 8 K in the spin-wave spectrum. The magnitude of magnetocaloric effect is similar to the values reported for most rare-earth based intermetallics. Characteristic behavior of the isothermal magnetic entropy change maximum points to a second-order character of the ferromagnetic phase transition in the compound studied.

The orthorhombic, space group Cmcm YbFe 2 Al 10 structure type series of compounds are known to form with practically the entire series of rare-earth elements R, but only with the three d − electron elements Fe, Ru, and Os. The Ce-derivatives in particular have been of much interest since the first reports of their highly unusual physical properties. Classified as Kondo insulators, CeRu 2 Al 10 and CeOs 2 Al 10 controversially order magnetically and with uncharacteristically high Neel temperatures of ≃ 28 K. CeFe 2 Al 10 on the other hand shows pronounced semiconducting and Kondo features but remains paramagnetic. As part of our ongoing studies into the rich physics of this class of materials we have succeeded in synthesizing new members of the 1:2:10 stoichiometry involving the chemical element Rh for the first time. CeRh 2 Al 10 is found to crystallize in the tetragonal system with space group I 4 1 / amd . Yb Rh 2 Al 10 on the other hand forms in the serial Cmcm orthorhombic structure type. We discuss important similarities between the two types. At 5.310 A the shortest Ce–Ce distance is, likewise to the situation in CeRu 2 Al 10 and CeOs 2 Al 10 , also well above the Hill limit of 3.40 A. Despite the cage-like structure and large rare-earth separation distances, this study reveals the onset of long-range magnetic ordering in CeRh 2 Al 10 at 3.9 K. The magnetic ordering develops out of an incoherent Kondo state that dominates the electrical resistivity below about 40 K.

We present an extended research on characterization of the ground state in a polycrystalline compound Ce2Ir3Al9 using powder x-ray diffraction, magnetic susceptibility χ(T), isothermal magnetization M(B), specific heat Cp(T), electrical resistivity ρ(T), magnetoresistivity ρ(B), thermoelectric power S(T) and thermal conductivity κ(T) measurements, together with a theoretical description of the obtained data to develop a more profound understanding of the physics in this compound. Ce2Ir3Al9 crystallizes in the orthorhombic Y2Co3Ga9-type of structure (space group Cmcm, No. 63, oC56, Z = 4). The χ(T) and Cp(T)/T data reveal the signatures of intermediate valence behaviour on Ce ions with the approximate value of the Kondo temperature TK = 96 K and the Sommerfeld coefficient γ = 31 mJ/mol ⋅ K2. In contrast to the magnetometric and thermodynamic measurements, the transport data (ρ(T) and S(T)) indicate the development of the Kondo lattice state. Accordingly, we expect that for Ce2Ir3Al9 the most likely scenario, which develops in a wide T range is the coexistence and competition of two energy scales of interactions between conduction electrons and 4f spins on Ce ions, located in one unique crystallographic site in the unit cell, in consequence carrying out our system from Ce4+ T e m p . → Ce3+. At higher temperatures, where the Kondo interaction becomes dominant the influence of the crystal electric field effect seems to play an influential role in the ground state of this compound too.

We report the magnetic, electronic and transport properties of the quasi-skutterudite compound Pr3Ir4Ge13 by means of magnetic susceptibility χ(T), electrical resistivity ρ(T), specific heat Cp(T), thermal conductivity κ(T), thermoelectric power S(T) and Hall coefficient RH(T) measurements. Pr3Ir4Ge13 does not show any phase transition down to 1.9 K. Magnetic, and specific measurements show that the system possesses a crystal electric field singlet ground state that is separated from the first excited state by about 37 K. ρ(T) shows a negative temperature coefficient of resistance for the whole temperature range studied and which can be explained in terms of Mott’s impurity band conduction mechanism. RH(T) measurements show that Pr3Ir4Ge13 is a low-carrier density semiconductor and its transport properties indicate a metallic-non metallic cross over behaviour. Large Seebeck coefficient was observed for the entire temperature range of investigation, and the analysis of temperature variation of S and S∕T showed no sign of strong correlation between the Pr 4f2 and conduction electron states near Fermi level.

Dc and ac – magnetic susceptibility (χ), specific heat ( C P ), electrical resistivity (ρ) and magnetoresistance measurements performed on the new polycrystalline compound Gd 2 AgSi 3 , crystallizing in the α – ThSi 2 tetragonal structure, are reported. Two magnetic phase transitions were observed in dc and ac susceptibility, specific heat and resistivity measurements at temperatures T N 1 = 11 K and T N 2 = 20 K, despite a single site occupied by Gd atom, which is an indication of the complex magnetic behavior. Gd 2 AgSi 3 turns out be one of the rare Gd compound in which a minimum is observed in the temperature dependence of resistivity in the paramagnetic state and also negative magnetoresistance over a wide temperature range (above T N 2 ), mimicking the behavior of exotic Gd 2 PdSi 3 , in this ternary family. The isothermal magnetic entropy change, adiabatic temperature change, and refrigerant capacity reach a value of 9.5 J/kg-K, 7.5 K and 302 J/kg, respectively for the change of magnetic field 0-9 T.

The alloys Ce 8 Pd 24 ( Al 1 − x Sn x ) with 0 ≤ x ≤ 1 were studied by means of electrical resistivity, thermal conductivity, thermoelectric power, magnetic susceptibility and magnetization measurements. In the entire composition range, an antiferromagnetic (AFM) long-range ordering has been established at low temperatures, with the Neel temperature increasing linearly from T N = 4.3 K for Ce 8 Pd 24 Al to T N = 7 K for Ce 8 Pd 24 Sn . Below T N , the electrical resistivity is dominated by scattering conduction electrons on spin-wave excitations. In the paramagnetic state, the electrical transport in the alloys with 0 ≤ x ≤ 0.7 reveals both coherent Kondo lattice scattering and crystal-electric field (CEF) effect, while that in the alloys with x ≥ 0.8 appears governed by CEF only. Above T N , all the alloys exhibit well localized magnetic behavior due to trivalent Ce ions. At high temperatures, the thermoelectric power can be interpreted in terms of a phenomenological resonance model giving an estimate of the CEF effect. The thermoelectric figure of merit of Al-rich alloys is small compared to those of commercial thermoelectric materials.

The superconducting phase transition at $$T_\mathrm{c} = 2.3$$ K was observed for the electrical resistivity $$\rho ({T})$$ and magnetic susceptibility $$\chi (T)$$ measurements in the ternary compound La $$_{5}\hbox {Ni}_{2}\hbox {Si}_{3}$$ that crystallizes in the hexagonal-type structure. Although a single-phase character with the nominal stoichiometry of the synthesized sample was confirmed, a small trace of the La–Ni phase was found, being probably responsible for the superconducting behaviour in the investigated compound. The magnetization loop recorded at $${T} = 0.5$$ K resembles a star-like shape which indicates that the density of the critical current can be strongly suppressed by a magnetic field. The low- $$T _{\rho }(T)$$ and specific heat $${C}_\mathrm{p}({T})$$ data in the normal state reveal simple metallic behaviour. No clear evidence of a phase transition to any long- or short-range order was found for $$C_\mathrm{p}(T)$$ measurements in the T-range of 0.4–300 K.

The effects of substituting moment-bearing Tb in CePt 2 Si 2 are reported through X-ray diffraction (XRD), electrical resistivity ( ρ ( T ) ), magnetic susceptibility, ( χ ( T ) ), and magnetization, ( σ ( μ 0 H ) ) measurements. XRD results for all compositions of ( Ce 1 − x Tb x ) Pt 2 Si 2 system indicate a tetragonal CaBe 2 Ge 2 - type structure with space group P 4 / n m m . ρ ( T ) results indicate a rapid evolution from a coherent Kondo lattice for the CePt 2 Si 2 parent compound to incoherent single-ion Kondo behaviour with substitution of Tb for Ce. However, between 90% and 100% of Tb content, the ( Ce 1 − x Tb x ) Pt 2 Si 2 system reverts back to stable local - moment, normal metal behaviour. χ ( T ) data at higher temperature follow the Curie - Weiss relation for all alloy compositions and give effective moment values μ e f f which increase gradually from the expected values of 2.54 μ B for the Ce 3 + - ion to 9.72 μ B for the Tb 3 + - ion. At low temperature χ ( T ) data exhibit antiferromagnetism at the N e ′ el temperature T N in the concentration range 0.7 ≤ x ≤ 1 . Below T N the zero-field-cooled and field-cooled susceptibility bifurcate in a 0.1 T field, suggesting an inhomogeneous magnetic ground state as a result of spin glass - like state for compositions in the range 0.6 ≤ x ≤ 1 . No evidence of metamagnetic behaviour was observed from σ ( μ 0 H ) data for all compositions.

The influence of Y- and La-substitution for Ce on the competing Kondo effect and magnetic ordering, as well as on spin dynamics in the Kondo semiconductor CeRu2Al10 have been investigated by means of thermal, electronic, and magnetic properties. The parent compound CeRu2Al10 is known to be a controversial antiferromagnet with high magnetic ordering temperature T 0 = 27 K. A small negative chemical pressure caused by La-doping results rapid suppression of T 0 and spin gap energy Δ m , compared to a small positive pressure caused by Y-doping. Upon Y- and La-doping, the electrical resistivity ρ(T) illustrates the evolution from dense Kondo semiconductor to incoherent single-ion Kondo behaviour, and hence weakens the c–f hybridization and thus lowers the Kondo temperature. The 5% Y- and La-doped compounds show enormous enhancement in the thermoelectric power and complex behaviour in the Hall resistivity below T 0 due to an abrupt change in charge carrier mobility with temperature. The magnetic contribution to electrical resistivity ρ mag(T) (≳50% La) and specific heat C P(T)/T (≳70% La) evidence non-Fermi-liquid behaviour at low temperature in the La-doped system, due to interplay of atomic disorder with spin-fluctuation. Application of magnetic field suppresses the spin-fluctuation in C P(T)/T and eventually emerges to Fermi-liquid state in the 95% La-doped compound in 9 T. The magnetic phase diagram illustrates that the strength of the Kondo interaction in the doped systems are primarily controlled by the effect of volume change as described by the compressible Kondo lattice model. We ascribe the fascinating observation of T K ≃ 4T 0 to anisotropy in the single-ion crystal electric field in the presence of strong anisotropic c–f hybridization.

We report the electrical and thermal transport properties of NdCu 4 Au and GdCu 4 Au compounds, crystallizing in the cubic MgCu 4 Sn - type crystal structure, with space group F 4 ¯ 3 m (no. 216).These properties are reported through measurements of electrical resistivity, ρ ( T ) , thermoelectric power, S ( T ) and thermal conductivity, λ ( T ) . ρ ( T ) and S ( T ) data indicate an antiferromagnetic (AFM)-like anomaly associated with a N e el temperature T N =3.9 K and 10.9 K for NdCu 4 Au and GdCu 4 Au compounds, respectively. ρ ( T ) data for both compounds shows a sudden drop at T N . Above T N , ρ ( T ) results are characteristic of an electron–phonon interaction in the presence of s − d scattering. Application of magnetic field slightly suppresses T N value in GdCu 4 Au compound from T N =10.9 K in a field of 0 T to 10.1 K in a field of 6 T. S ( T ) data at low temperatures for both compounds shows a minimum at T N . Critical analysis of S ( T ) in terms of the phenomenological resonance model yield the positions ( E f ) and bandwidths ( W f ) of the 4 f - band in both compounds: E f =3.81(6)K, W f =329(58) K for the Nd compound and E f =18.2(4) K, W f =306(5) K for the Gd compound. λ ( T ) for both compounds decreases linearly upon cooling from room temperature. The reduced Lorentz number L / L 0 deviates from the Wiedmann–Franz at low temperature with a strong increase in L / L 0 upon cooling the samples from room temperature.

The robust field-insensitive heavy fermion features in Sm3 Ru4 Ge13 and the magnetic phase transition at TN ≈ 5 K are studied using magnetization M(T), specific heat Cp(T), resistivity ρ(T) and thermal conductivity κT(T). The average crystal structure of Sm3 Ru4 Ge13 conforms to the cubic space group P m 3 ¯ n however, signatures of subtle structural distortions are obtained from the x ray data. The magnetic susceptibility, χ(T), follows a modified Curie–Weiss law indicating the presence of crystal fields of Sm3+ and the significance of van Vleck terms. No sign of ferromagnetism is observed in M(H) of Sm3 Ru4 Ge13 which yields only 0.025 μB/f.u.-Sm at 2 K, 7 T. The Sommerfeld coefficient, γ≈ 220 mJ/mol-Sm K2, estimated from the analysis of low temperature specific heat suggests the formation of heavy quasi particles at low temperature. Though a lnT dependence of ρ(T) is observed till 60 K, the resistivity behavior is accounted for by assuming a two-band model for activated behavior of charge carriers. The field scans of resistivity, ρ(H), below TN display significant nonlinearity while those above the TN are more metal-like. Low values of thermal conductivity, κT(T), are observed in Sm3 Ru4 Ge13 however, displaying an anomaly at TN which signifies magnetoelastic coupling. A fairly high value of Seebeck coefficient, S ≈ 40 μV/K is observed at 300 K. We identify Sm3 Ru4 Ge13 as a low charge carrier density system with unusual field-insensitive heavy fermion features very similar to the filled skutterudites.

We report the crystal structure as well as the magnetic, electronic and transport properties of PrCu2Au3 which crystallizes in the MgCu4Sn-type structure with the cubic space group F 4 ¯ 3 m (No. 216). In this structure, the Pr3+ ion sits on a lattice site with the cubic T d symmetry which dictates the crystal electric field (CEF) splitting of the Hund’s 3H4 ground multiplet into four levels. The sample has been investigated by measurements of temperature dependences of specific heat, C p ( T ) , electrical resistivity, ρ ( T ) , magnetic susceptibility, χ ( T ) , isothermal magnetization, M ( B , T ) , thermal conductivity, κ T ( T ) and thermoelectric power, S ( T ) . χ ( T ) follows a Curie-Weiss behavior above 100 K with an effective magnetic moment, μ eff = 3.3 μ B /Pr which is comparable to a calculated value of 3.58 μ B /Pr for a free Pr3+ ion and a Weiss temperature, θ CW = 15.70 K indicating a dominant ferromagnetic interaction. From the analysis of M ( B , T ) and the 4f-electron derived specific heat ( C 4 f ( T ) ) results, the CEF ground state is a Γ 5 magnetic triplet and the CEF energy scheme is presented. The Sommerfeld coefficient, γ estimated from the low-temperature C 4 f ( T ) is 304 mJ/(mol K2) indicating a mass enhancement of the conduction electrons at low temperatures. Further analysis of the heavy fermion properties based on the Sommerfeld-Wilson ratio supports the formation of a heavy fermion state in PrCu2Au3. However, the absence of an enhancement in S / T at low temperatures possibly suggests a weak correlation between the conduction electrons and the 4 f -electrons at the Fermi energy. The thermal transport properties suggest that PrCu2Au3 is likely a compensated metal.

In the last few decades there has been growing interest in studying Mott insulators due to their ability to host novel quantum phenomena when the system is perturbed by various stimuli. Recently the antiferromagnetic Mott insulator Ca2RuO4 has received considerable attention due to superconductivity and metal-insulator transition induced by pressure and electric field respectively. Here we report the details of the synthesis of a novel systems made by Ca2RuO4 and Ru metal inclusions. Samples with lamellae, rods and globules of Ru embedded in Ca2RuO4 single crystals were successfully synthesized by floating zone technique with an excess of Ru in the starting material. The morphology and structural studies revealed a randomly orientated distribution of the shining Ru inclusions with an average size of few microns. Magnetic and electrical properties showed a behavior similar to the one observed in single crystals with the only Ca2RuO4 phase. We also measured the current-voltage characteristics of the whole Ca2RuO4–Ru system and of a single Ru rod by electric micro-contacts estimating the room temperature resistivity of the Ru embedded inclusions. This study shows that physical properties of Ca2RuO4–Ru metal system are related to the properties of the constituent phases, similarly to the case of Sr2RuO4–Ru metal.

Here we report the magnetic, electronic and thermal transport properties of the heavy-fermion semimetal Pr3Os4Ge13 with a cage-like structure by means of magnetic susceptibility, χ(T), isothermal magnetization, M(B, T), electrical resistivity, ρ(B, T), Hall coefficient, R H(T), specific heat, C p(T), thermal conductivity, κ(T) and thermoelectric power, S(T). ρ(T) and R H(T) show semimetallic features in a manner that mimics a thermal activated behaviour with an activation energy, Δ/k B = 6.5 K indicating the opening of a small energy gap in the material. At low temperatures, a Sommerfeld coefficient, γ = 128 mJ (mol-1 K-2) observed indicates a mass enhancement of the quasiparticles at low temperatures which bears witness to a heavy fermion state in Pr3Os4Ge13. A Wilson-Sommerfeld ratio, W R and the dimensionless ratio, S/γT of 1.01 and 0.62 ± 0.018 observed, respectively, are in good agreement with the Fermi liquid scenario. S(T) and R H(T) reveal hole dominated transport (p-type material) with a relatively large room temperature value of S(T) = 32.85 ± 0.98 μV K-1. A room temperature low value of κ(T) = 1.61 W K-1 m-1 leads to a thermoelectric figure of merit, ZT = 0.03 ± 0.001 which is comparable to values achieved in several clathrates around the same temperature. Features from S(T) and ρ(T) favour the realization of a higher ZT value at elevated temperatures.

We report the investigation of the magnetic susceptibility (χ), specific heat (CP), electrical resistivity (ρ) and magnetoresistance (MR) studies of the compound Ce2Ru3Ge5. Ce2Ru3Ge5 crystallizes i...

Transition effects from magnetically ordered Kondo lattice (KL) behaviour in CeAu 2 Si 2 to intermediate valence (IV) behaviour in CeNi 2 Si 2 have been investigated by substitution of Au with Ni. These investigations were done through measurements of the lattice parameters, electrical resistivity ( ρ ( T ) ), magnetisation ( M ( μ 0 H ) ) and magnetic susceptibility ( χ ( T ) ) on the Ce(Au 1− x Ni x ) 2 Si 2 ( 0 ≤ x ≤ 1 ) series. Lattice parameters as derived from XRD measurements deviate from Vegard's rule around x =0.6–0.8. ρ ( T ) data indicate KL behaviour in the presence of a crystal field for x ≤ 0.6 , the occurrence of magnetic ordering for x ≤ 0.2 and valence fluctuation for x ≥ 0.8 . χ ( T ) data at high temperatures, follow the Curie–Weiss relation for alloys in the concentration 0 ≤ x ≤ 0.6 (KL region) and give effective magnetic moment values μ eff close to that expected for free Ce 3+ ion. The low temperature χ ( T ) data indicate the onset of antiferromagnetic ordering for x ≤ 0.2 . For alloys in the concentration range 0.8 ≤ x ≤ 1 , the χ ( T ) behaviour is reminiscent of intermediate valence (IV) systems. M ( μ 0 H ) measurements indicate metamagnetic behaviour for alloys in the concentration range 0 ≤ x ≤ 0.1 .

Results of magnetic, specific heat, electric and thermal transport studies carried out on the novel hexagonal-type structure Ce6Pd12In5 compound, with a unique site for Ce, two sites for In and four sites for Pd are reported. The compound exhibits long-range order, probably of antiferromagnetic type, below T N = 1.6 K in spite of a moment reducing Kondo effect acting on the magnetic Ce3+ ions. A strong influence of magnetic field on the low temperature dependencies of susceptibility, specific heat and electrical resistivity is observed. The crystal-electric field effect, CEF, plays an influential role in the ground state of this compound. The CEF parameters have been estimated. Based upon the low-temperature specific heat we observe heavy fermion behavior with the electronic specific heat coefficient that is enhanced to the value of γ = 132 mJ/Ce-mol K2. In the electrical resistivity, a logarithmic character ρ 4 f ( T ) ∼ - ln T is observed that arises from incoherent Kondo scattering. Towards low temperature this behavior evolves into Kondo lattice formation with a coherence temperature T coh ≃ 5.3 K, before long-range order takes place. We propose that Ce6Pd12In5 presents a new case study for competing Kondo and magnetic ordering in a high-symmetry lattice, with CEF and magnetocrystalline anisotropy further impacting upon the cooperative magnetic behavior.

It was recently suggested that for the Cr 1 − x Al x alloy system the Sommerfeld specific heat coefficient ( γ ) as a function of x may peak at the triple point (TP) concentration ( x t ) of the x– T magnetic phase diagram. The TP at ( x t , T t ) represents the intersection point of three magnetic phase transition lines at which incommensurate (I) and commensurate (C) spin-density-wave (SDW) phases are expected to coexist with the paramagnetic (P) phase. A comprehensive experimental study on the physical properties of single crystalline Cr 1 − x Al x alloys in the concentration range 0 ⩽ x ⩽ 0.034, that encloses x t , is reported here for further investigations of the above conjecture and possible anomalous behaviour in other physical properties near x t . The measurements include the electrical resistivity ( ρ ), Seebeck coefficient ( S ), specific heat ( C p ), Hall coefficient ( R H ), magnetic susceptibility ( χ ) and thermal conductivity ( κ ). All these properties, except for κ , depict anomalous temperature and concentration dependencies of SDW origin for x close to x t . The present study indicates a value of x t rather close to x = 0.022. The x -dependence of γ exhibits an extraordinary large and sharp peak near this concentration. This observation is interpreted as indication that the temperature of the TP is likely situated at 0 K. A new magnetic phase diagram is therefore proposed for the Cr 1 − x Al x alloy system for x in the region of x t . This study presents novel experimental evidence of exceptional anomalous magnetic behaviour around the TP concentration of the Cr 1 − x Al x system. It should incite similar studies on other Cr alloy systems with a TP on their magnetic phase diagrams.

An investigation of the magnetic entropy change ΔSM and resistivity ρ, and the relation between them, for La0.7Ca0.3MnO3 (LCMO) material has been presented. By using an equation of the form Δ S M = − α ∫ 0 H [ δ ln ( ρ ) δ T ] H d H (α=9.98 emu/g), which relates magnetic order to transport behavior of the compounds, we measure the magnetic entropy change ΔSM from the resistivity measurement, where the resistivity results agree quite well with the fitting parameter α=9.98 emu/g in the intermediate temperature range. This result reveals the predominant role of magnetic polarons on the magnetoresistive property of manganites. It is obvious that magnetic disorder, characterized by ΔSM, affects the magnetic polarons, while the magnetic polarons influence the electronic transport properties, which may be the underlying reason for a salient ΔSM−ρ relation. It also provides an alternative method to determine magnetic entropy change on the basis of resistive measurements.

Transport and thermodynamic properties of the well-ordered hexagonal CeAuGe compound have been studied. This compound is known to order ferromagnetically at TC = 10 K with well-de ned anomalies in magnetic susceptibility χ(T ), electrical resistivity ρ(T ) and speci c heat Cp(T ) characterising the phase transition. The location of TC has been observed to be unstable and enhanced even in moderate applied magnetic elds. However, the dilution of magnetic species, Ce, with the non-f electron element, La, is shown in this work to achieve a continuous suppression of TC to 0 K. The integrity of the space group and the details of the unit cell occupation are retained throughout the substitution series, as is the high-temperature localized Ce-e ective magnetic moment μeff = 2.54 μB/(mol Ce). Our studies of physical properties down to 0.05 K show a quantum critical form of nonFermi liquid behaviour, characterised by a logarithmic divergence in Cp(T )/T data in the very dilute Ce content.

We report on the synthesis, crystallographic analysis, and physical properties of the new intermetallic compound CePd4Sn. It crystallizes in the orthorhombic Cmce space group with cell dimensions a = 9.003(4) angstrom, b = 23.613(3) angstrom, c = 8.265(3) angstrom, Z = 16, Pearson code oS96 and adopts a site exchange variant of the Dy2Ni7Sn3 type. Chemical bonding is characterized by strong Pd-Pd and Pd-Sn interactions. The structure can be presented as a packing of condensed cerium polyhedra. The 4f-electron part of the electrical resistivity is in evidence of incoherent Kondo scattering near and below room temperature that originates from the Ce3+ local moment. The magnetic susceptibility demonstrates stable moment behavior down to similar to 100 K. Magnetic ordering, presumably of an antiferromagnetic nature, occurs below T-N = 0.9 K. (C) 2013 Elsevier B.V. All rights reserved.

YFe2Al10 forms in a well-ordered crystal structure, with a unique site for the magnetic atom Fe. At elevated temperatures YFe2Al10 behaves electronically as a good metal. At low temperatures on the other hand, signatures of correlated behavior develop and eventually non-Fermi-liquid scaling dominates all of the physical properties: the electrical resistivity develops a negative temperature coefficient below 20 K, and the specific heat Cp(T)/T and χ(T) both assume a power-law increase upon lowering the temperature below ≃3 K. Lowest temperature studies have failed to find magnetic ordering in YFe2Al10 in spite of compelling evidence that there is impending order in this compound and that it is indeed of ferromagnetic character. Here we report on measurements of thermal and electronic transport as well as heat capacity studies on the series of compounds YFe2 + δAl10 with δ ≤ |0.1|, with the purpose of testing the stability of the low-temperature divergences in physical properties against off-stoichiometric Fe.

We report on magnetotransport properties of the Kondo semiconducting compound ${\mathrm{CeRu}}_{2}{\mathrm{Al}}_{10}$, focusing on its exotic phase below ${T}_{0}=27$ K. An excess thermal conductivity $\ensuremath{\kappa}$ emerges below ${T}_{0}$ and is gradually suppressed by magnetic field, strikingly resembling those observed in the hidden-order phase of ${\mathrm{URu}}_{2}{\mathrm{Si}}_{2}$. Our analysis indicates that low-energy magnetic excitation is the most likely origin, as was also proposed for ${\mathrm{URu}}_{2}{\mathrm{Si}}_{2}$ recently based on inelastic x-ray scattering measurements of phonon dynamics, despite the largely reduced magnetic moments. Likewise, other transport properties such as resistivity, thermopower, and Nernst effect exhibit distinct features characterizing the very different charge dynamics above and below ${T}_{0}$, sharing similarities to ${\mathrm{URu}}_{2}{\mathrm{Si}}_{2}$, too. Given the exotic nature of the ordered phase in both compounds, whether a unified interpretation to all these observations exists appears to be extremely interesting.

The heavy fermion compound Ce3Pd20Si6 displays unconventional quantum criticality as the lower of two consecutive phase transitions is fully suppressed by magnetic field. Here we report on the effects of pressure as an additional tuning parameter. Specific heat and electrical resistivity measurements reveal a converse effect of pressure on the two transitions, leading to the merging of both transitions at 6.2 kbars. The field-induced quantum criticality is robust under pressure tuning. We rationalize our findings within an extended version of the global phase diagram for antiferromagnetic heavy fermion quantum criticality.

We present results of physical properties studies of the new cerium compound Ce2Pt9Al16. The crystal structure may be described in terms of cerium-filled atomic cages. Magnetic susceptibility indicates that the magnetism in this compound originates from a stable local moment in trivalent cerium. Incoherent Kondo scattering is evident in the electrical resistivity close to room temperature. The combined results of susceptibility, resistivity and heat capacity show that 4f-spins in Ce2Pt9Al16 produce three successive magnetic phase transitions at low temperatures. Using applied magnetic fields we demonstrate how details of the ground state can be manipulated.

CeCu 5 is a Kondo lattice in which antiferromagnetic ordering occurs at 3.9 K. Substituting Cu with Al to achieve CeCu 3 Al 2 results in amplifying the Kondo interaction through addition of conduction electrons, and simultaneously driving the magnetic order down to beyond detection. We present results of specific heat and electrical resistivity that argue for the existence of non-Fermi-liquid behavior founded in a magnetic quantum critical point in CeCu 3 Al 2 .

A first report of physical properties of the ternary intermetallic compound CeRu2Al10 is given. The electrical resistivity below room temperature shows activated behaviour with a narrow gap of Δ ≃ 20 K before the onset of a sharp peak in ρ ( T ) below T * = 27 K . The Hall coefficient as well as the thermoelectric power are overall positive, and both increase in a similarly sharp manner below T * . The lattice part of the thermal conductivity indicates phonon coupling of the heat transport at T * , possibly underlying a lattice transformation that accompanies the putative metal-to-insulator and magnetic phase transitions.

The effects of boron doping and electron correlation on the transport properties of CVD boron-doped multiwalled carbon nanotubes are reported. The boron-doped multiwalled carbon nanotubes were characterized by TEM as well as Raman spectroscopy using different laser excitations (viz. 488, 514.5 and 647 nm). The intensity of the D-band laser excitation line increased after the boron incorporation into the carbon nanotubes. The G-band width increased on increasing the boron concentration, indicating the decrease of graphitization with increasing boron concentration. Electrical conductivity of the undoped and boron-doped carbon nanotubes reveal a 3-dimensional variable-range-hopping conductivity over a wide range of temperature, viz. from room temperature down to 2 K. The electrical conductivity is not found to be changed significantly by the present levels of B-doping. Electron Paramagnetic Resonance (EPR) results for the highest B-doped samples showed similarities with previously reported EPR literature measurements, but the low concentration sample gives a very broad ESR resonance line.

We report on the effects that different applied magnetic fields have on the electrical resistivity and the Hall coefficient in single crystals of the ferromagnetic Kondo lattice CeAgSb 2 . The total measured Hall coefficient R H shows a large field-dependent anomaly at T C = 9.5 K . We resolved R H into its normal and anomalous components in order to address the question of the evolution of R H when T C is suppressed to zero by an applied magnetic field.

A number of compounds of structural formula RRu 4 Sn 6 (R=rare-earth element) have previously been reported to form in the tetragonal crystal structure with space group I4¯2m. In this structure the R atoms are well isolated from each other. We embarked on this study to investigate the physical properties and to compare with earlier results obtained on the strongly correlated, low charge-carrier density compound CeRu 4 Sn 6 . Here we report our results of crystallographic, electrical resistivity, and magnetic studies on this family of compounds. In contrast to the behaviour in CeRu 4 Sn 6 , magnetic ordering is evident at low temperatures in the compounds with R=Sm, Gd, and Dy, as is evidenced by well-resolved anomalies in the temperature dependence of the electrical resistivity and static magnetic susceptibility.

The occurrence of a maximum at a temperature T max in the resistivity of the dense Kondo compound CeNiAl4 and in (Ce1−xY x)NiAl4 alloys is investigated. T max ( ∝ T K , the Kondo temperature) first increases, goes through a maximum value and decreases with increase in x . This behaviour is qualitatively explained by considering the competing influence of volume changes and dilution (the Kondo-hole effect) on the Kondo system. Complementary magnetic susceptibility measurements corroborate these results.

Ce3Pd20Si6 forms in a cubic crystal structure with the cerium atoms located on two different sites, both of cubic point symmetry, resulting in two interleaved cubic cerium sublattices. We present here the results of detailed low-temperature specific heat and electrical resistivity measurements taken in magnetic fields up to 14 T, with the purpose of shedding light on the complex low-temperature behaviour that was alluded to in previous literature reports on this compound. Our specific heat data show two phase transitions, at TL(B = 0) = 0.31 K and at TU(B = 0) = 0.5 K respectively, probably of magnetic origin, and with distinctly different response to applied magnetic fields. TL is shifted towards lower temperatures and becomes indiscernable in fields above 1 T. TU on the other hand is shifted upward and disappears in fields above 8 T. The electrical resistivity data follow a Δρ ∝ T5/3 power-law behaviour below TU for a limited range in field, suggestive of spin fluctuations near a three-dimensional ferromagnetic quantum phase transition.

We have synthesized polycrystalline Sr2IrO4 and measured its magnetic susceptibility, electrical resistivity, specific heat, Seebeck coefficient, and thermal conductivity. The magnetic susceptibility χ(T) shows a ferromagnetic transition at 250 K while the behaviour above the transition temperature is well described by a Curie–Weiss fit with a small effective moment μeff = 0.33 μB and a paramagnetic Curie–Weiss temperature, θCW = +251 K, consistent with previous studies on this compound. However, specific heat, Seebeck coefficient, and thermal conductivity are all dominated by the phonon contribution and show no anomalies at the ferromagnetic transition. Electrical resistivity, unlike the single crystal, shows a huge increase, three orders of magnitude, with decreasing temperature. The temperature dependence of resistivity is logarithmic at high temperatures (210 K

Measurements of electrical resistivity are presented for polycrystalline alloys in the CePt 2 (Si 1− x Sn x ) 2 system. Results of X-ray diffraction indicate that the tetragonal region of the CePt 2 (Si 1− x Sn x ) 2 alloy system that is amenable for study only extends up to x =0.3. The resistivity maximum characteristic of a Kondo lattice is observed at a temperature T max =63 K for the parent compound CePt 2 Si 2 and shifts to lower temperatures with increase in Sn content. The compressible Kondo lattice model is applied to describe the results of T max in terms of the on-site Kondo exchange interaction J and the electron density of states at the Fermi level N ( E F ). A value of | JN ( E F )|=0.060±0.009 for the parent compound is obtained from the experimental results.

The electronic and magnetic properties of the ternary cerium compounds Ce 2 PdGe 6 and Ce 2 PtGe 6 are reported within the context of measurements of electrical resistivity, magnetoresistivity, and magnetic susceptibility. Ce 2 PdGe 6 orders magnetically at T N = 11.5 K , and Ce 2 PtGe 6 at T N = 9.9 K . In the ordered region, the magnetization as well as the magnetoresistance reveal anomalous behaviour for both compounds, which are ascribed to metamagnetic transitions into a field-induced ferromagnetic state.

The influence of substituting Ce with La in the Kondo compound CeCu5In has been investigated using x-ray diffraction, specific heat (Cp), electrical resistivity (?(T)), magnetoresistivity?(MR) and thermoelectric power?(TEP) measurements. Cp of CeCu5In and the (Ce1?xLax)Cu5In alloys shows enhanced values at low temperatures. Between?10 and 20?K the equation Cp/T = ?conv+?T2 fits the data for all alloys with ?conv scaling linearly with Ce concentration. Below 10?K a pronounced upturn in Cp values occurs. Susceptibility data above 100?K follow the Curie?Weiss relation and give effective moment ?eff values in fair agreement with that of a Ce3+-ion. The ?(T) studies illustrate the evolution from Kondo lattice to single-ion Kondo behaviour with increase in La content in the (Ce1?xLax)Cu5In alloy series. MR measurements on Ce dilute alloys are interpreted within the single-ion Bethe ansatz description and values of the Kondo temperature TK are calculated. A compressible Kondo lattice model has been used to describe the decrease in TK and in Tm? (the temperature at which a maximum in ?(T) occurs for the coherent dense Kondo alloys) with decrease in Ce concentration for these alloys. The TEP is positive and shows a maximum at approximately 45?K for several investigated (Ce1?xLax)Cu5In alloys.

Resistivity ρ ( T ), magnetoresistivity Δ ρ / ρ , and magnetic susceptibility χ ( T ) measurements on a single crystal of the non-magnetically ordered Kondo semimetal U 2 Ru 2 Sn are presented. The resistivity is highly anisotropic and yields band-gap values according to an activation-like description that differ by two orders of magnitude depending on the current direction. The temperature dependence of magnetoresistivity for both perpendicular arrangements ( j ∥c, B ∥a, or j ∥a, B ∥c ) renders the same behavior (Δ ρ / ρ positive with a peak near 25 K). In the longitudinal arrangement, j ∥c∥ B , the magnetoresistivity is much smaller and changes sign at the temperature of a knee in ρ ( T ) at 30 K.

We present the results of exploratory measurements of the electrical resistivity ρ ( T ), magnetoresistivity MR, magnetic susceptibility χ ( T ), and specific heat C ( T ) on polycrystalline Ce 3 Pd 5 Si. The temperature variation of ρ ( T ) and of χ ( T ) from room temperature down to ∼10 K indicate largely normal-metal behaviour. Below 10 K ρ ( T ) decreases rapidly with lowering temperature and displays a knee at 3.5 K. χ ( T ) remains Curie–Weiss-like down to 100 K, with the paramagnetic Curie temperature of +12.7 K, and the effective magnetic moment of 2.37 μ B /mol Ce . At lower temperatures the inverse susceptibility χ −1 ( T ) reveals crystal field effects but no anomaly hinting that magnetic phase transition is seen down to 1.7 K. The MR is large and negative below 30 K. In C ( T ) there is an upturn towards very large values at low temperatures, and an anomaly is seen at 3.5 K, typical of magnetic ordering.

UPtSn is known as a semimetal with a bandgap in the electronic density of states. We report the results of measurements of the cubic lattice parameter a(T), coefficient of thermal expansion α(T), magnetic susceptibility χ(T), magnetization σ(T,B), specific heat C(T) and electrical resistivity ρ(T, B). We give arguments that this compound is antiferromagnetically ordered with T N = 35 K, although this is not confirmed by neutron diffraction. For carefully annealed samples of UPtSn we provide a phenomenological description of electron transport properties in terms of the fact that the temperature-dependent bandgap is closed at T = 0 K. Results of electrical measurements on the isostructural compounds ThPtSn and ZrPtSn provide evidence for bandgap formation in these two compounds as well.

The anomalous properties of Ce2Rh3Al9 and of U2Rh3Ga9 are investigated by magnetoresistivity (MR) measurements of these alloys and of their non-f electron counterparts La2Rh3Al9 and Th2Rh3Ga9 between room temperature and T=1.4 K , and in magnetic fields up to 8 T. In U2Rh3Ga9 there is a large, negative MR prevalent up to 80 K where the electrical resistivity ρ(T) reaches a maximum. The MR in Ce2Rh3Al9 is small and negative below 8 K, then turns positive at the shoulder-like anomaly in ρ(T) and remains positive towards the peak seen in ρ(T≃140 K ). The analysis of MR(T,B) for U2Rh3Ga9 in the paramagnetic Kondo-lattice region yields a Kondo temperature of T K =5.3(1) K which is of the same order as the magnetic ordering temperature.

The results of the magnetic, electron transport, heat capacity and heat conduction measurements on the new rhombohedral ternary compound Pr2Rh3Ge have been investigated. The synthesized polycrystalline compound was found to crystallize in the ternary ordered variant of the cubic Laves phase [Formula: see text]-type of structure with the space group R[Formula: see text]m, as previously reported. Pr2Rh3Ge exhibits a ferromagnetic behaviour below [Formula: see text] K, which was found to be unstable in low applied magnetic fields, revealing characteristics usually attributed to the long-range order. In the entire paramagnetic region electrical resistivity shows monotonous metallic conductivity character. We estimated that the Sommerfeld coefficient γ = 315 mJ/Pr-mol · [Formula: see text] of [Formula: see text] [Formula: see text]Ge is very large with comparison to ordinary metals which indicate the existence of heavy fermion behaviour of itinerant charge carriers at low temperatures or enhanced density of the quasi-particle state at the Fermi level. The crucial role of the crystalline electric field effects on the ground state properties of [Formula: see text] (J = 4) has been also observed. We think that the heavy fermion behaviour in [Formula: see text] [Formula: see text]Ge results from the dynamic low-lying crystal-field fluctuations, since there is no sign of Kondo effect in electrical resistivity and no enhancement of the slope S(T)/T in thermoelectric power data at low temperatures. It suggests that the conduction electrons at the Fermi level does not correlate with the 4f 2 states of [Formula: see text] atoms and hence there is no place for a typical spin Kondo effect, as it is commonly observed in Ce- and Yb-based heavy fermion systems.

The influence of electron doping on semimetallic SrFBiS2 has been investigated by means of resistivity, zero and transverse - field (ZF/TF) muon spin relaxation/rotation (μSR) experiments. SrFBiS2 is semimetallic in its normal state and small amounts of La doping results in bulk superconductivity at 2.8 K, at ambient pressure. The temperature dependence of the superfluid density as determined by TF-μSR can be best modelled by an isotropic s - wave type superconducting gap. We have estimated the magnetic penetration depth [Formula: see text] nm, superconducting carrier density [Formula: see text] carriers m-3 and effective-mass enhancement m * = 1.558 m e. Additionally, there is no clear sign of the occurrence of spontaneous internal magnetic fields below [Formula: see text], which implies that the superconducting state in this material can not be categorized by the broken time-reversal symmetry which is in agreement with the previous theoretical prediction.

Electrical resistivity, ρ(T), measurements on U2Ru2Sn show typical Kondo semiconducting behaviour, namely a ρ(T)~ln T behaviour at higher temperatures and an activation-like increase in ρ(T) below 20 K which indicates the opening of a small gap in the electronic density of states. The magnetic susceptibility, χ(T), of U2Ru2Sn has a maximum around 180 K which is characteristic of intermediate-valence behaviour. The χ(T) data for U2Ru2Sn have been fitted to the interconfigurational fluctuation model of Sales and Wohlleben giving a value of Tsf* = 155(2) K for the characteristic fluctuation temperature. Substituting as little as 5% Th for U leads to a ρ(T) variation reminiscent of that of a single-ion Kondo metal ρ(T) = ρ(0)[1-(π2/16)(T2/TK2)]. Values of TK = 79(1) and 113(1) K are respectively obtained for alloys with 5% and 10% Th substitution.

Electrical resistivity, thermoelectric power and specific heat measurements are reported for a Cr+2.2 at% Al alloy single crystal, having an Al content close to the triple point on the magnetic phase diagram of the Cr–Al alloy system. A weak resistivity component of spin-density-wave origin, not previously observed in alloys near the triple point concentration, is isolated at low temperatures. Its presence is confirmed by the thermoelectric measurements. The specific heat measurements suggest a maximum in the density of states at the Fermi energy for alloy concentrations close to the triple point, a point that appears to be a particular type of critical point for the Cr–Al alloy system.

The temperature dependences of DC and AC magnetisation, electrical resistivity and magnetoresistivity of TbCu4Ag and DyCu4Ag are reported. In contrast to previous studies which indicate TbCu4Ag to be a simple antiferromagnet and DyCu4Ag to be a ferromagnet, our study indicates a more complicated behaviour for these materials. We observe three magnetic transitions for TbCu4Ag, viz. at TC=20 K, T1=11 K and T2=2.5 K. At temperatures T⩽ 10 K the magnetic isotherms show metamagnetic behaviour, while for T1⩽T⩽TC our results suggest canted antiferromagnetism. For DyCu4Ag magnetic transitions are observed at TC=19 K and in the vicinity of 5 K. Also for this material there is evidence suggesting a canted antiferromagnetic spin structure.

The results of electrical resistivity ρ(T) and magnetoresistivity MR(T, B) for K and T are reported for the (Ce1-xNdx)Cu6 alloy system. For small Nd substitutions in the heavy-fermion CeCu6 parent compound, the Kondo lattice is characterized through coherence effects in ρ(T) at low temperatures. The ρ(T) data above room temperature are used to resolve the electron-phonon scattering, and it is indicated that the single-ion Kondo interaction dominates both ρ(T) and MR(B) for a wide range of intermediate Ce concentrations. Based on this, the MR(B) data for different isotherms and alloy compositions are analysed according to the Bethe- ansatz description. We also discuss the observed deviations of our data from the preceding theoretical description due to the onset of magnetic order in alloys with high Nd content, and to phase coherence at low temperatures.

Measurements of electrical resistivity ρ ( T ) , magnetoresistivity MR and magnetic susceptibility χ ( T ) are reported for the pseudo-ternary alloys ( Ce 1 - x Y x ) Pt 2 Si 2 . ρ ( T ) results reveal coherent Kondo scattering above 80% Ce concentration and a rapid evolution to single-ion Kondo scattering with an increase in Y concentration x. MR measurements on Ce alloys in the single-ion Kondo region are analyzed on the basis of calculations by Schlottmann for the Bethe-ansatz solution in the context of the Coqblin–Schrieffer model. The analysis yields values of the Kondo temperature T K and the effective moment of the Kondo ion μ K . χ ( T ) data above 120 K follow the Curie-Weiss relation for all the investigated concentrations and give effective moment values μ eff in close agreement with μ eff = 2.54 μ B expected for the Ce 3 + -ion.