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Correa, V. F., A. G. Villagrán Asiares, D. Betancourth, S. Encina, P. Pedrazzini, P. S. Cornaglia, García D.J., J. G. Sereni, B. Maiorov, N. Caroca-Canales et al. "Strong magnetoelastic effect in CeCo1âˆ’xFexSi as Néel order is suppressed." Physical Review B 100 (2019): 184409.
Abstract: A very strong magnetoelastic effect in the CeCo1âˆ’xFexSi alloys is reported. The strength of the magnetostrictive
effect can be tuned upon changing x. The moderate low-temperature linear magnetostriction observed at low
Fe concentrations becomes very large (L
L (16T, 2K) = 3 Ã— 10âˆ’3) around the critical concentration xc â‰ˆ 0.23 at
which the long-range antiferromagnetic order vanishes. Upon increasing doping through the nonmagnetic region
(x > xc), the magnetostriction strength gradually weakens again. The interplay between magnetic order and the
Kondo screening appears to cause an enhanced valence susceptibility slightly changing the Ce ions valence,
ultimately triggering the large magnetostriction observed around the critical concentration. Previous studies
of the evolution of the lattice parameters with x as well as magnetization and x-ray absorption spectroscopy
measurements support this hypothesis.
Correa, V. F., D. Betancourth, J. G. Sereni, N. Caroca-Canales, and C. Geibel. "Remarkable magnetostructural coupling around the magnetic transition in CeCo0.85Fe0.15Si." Journal of Physics: Condensed Matter 28, no. 34 (2016): 346003.
Abstract: We report a detailed study of the magnetic properties of CeCo0.85Fe0.15Si under high magnetic
fields (up to 16 Tesla) measuring different physical properties such as specific heat, magnetization,
electrical resistivity, thermal expansion and magnetostriction. CeCo0.85Fe0.15Si becomes
antiferromagnetic at TN 6.7 K. However, a broad tail (onset at TX 13 K) in the specific heat
precedes that second order transition. This tail is also observed in the temperature derivative of
the resistivity. However, it is particularly noticeable in the thermal expansion coefficient where it
takes the form of a large bump centered at TX. A high magnetic field practically washes out that tail
in the resistivity. But surprisingly, the bump in the thermal expansion coefficient becomes a well
pronounced peak fully split from the magnetic transition at TN. Concurrently, the magnetoresistance
also switches from negative to positive above TN. The magnetostriction is considerable and
irreversible at low temperature ( (16T)4Ã—10âˆ’ L
4 at 2 K) when the magnetic interactions
dominate. A broad jump in the field dependence of the magnetostriction observed at low T may be
the signature of a weak ongoing metamagnetic transition. Taking altogether the results indicate the
importance of the lattice effects on the development of the magnetic order in these alloys.
Custers, J., T. Cichorek, P. Gegenwart, N. Caroca-Canales, O. Stockert, C. Geibel, F. Steglich, P. Pedrazzini, and J. G. Sereni. "Non-Fermi liquid effects close to a QCP in CeIn3-xSnx." ACTA PHYSICA POLONICA B 34, no. 2 (2003): 379–382.
Abstract: Resistivity and specific heat measurements at low temperatures on CeIn3-xSnx samples with concentrations x = 0.6, 0.65 and 0.7 demonstrate that with increasing Sn-alloying, the antiferromagnetic ordering temperature decreases continuously down to T = 0 K and disappears at a quantum critical point. We observe non-Fermi liquid (NFL) behavior in the resistivity and the specific heat, however the temperature dependencies are different from the predictions for a spin density wave (SDW) scenario. The resistivity at the critical point shows e.g., a linear temperature dependence, as expected for two dimensional fluctuations, which however can be excluded in the cubic structure of CeIn3-xSnx.
Deppe, M., N. Caroca-Canales, J. G. Sereni, and C. Geibel. "Evidence for a metamagnetic transition in the heavy Fermion system CeTiGe." In Journal of Physics: Conference Series, 012026. Vol. 200. International Conference on Magnetism, ICM 2009 200, no. SECTION 1. Karlsruhe, 2010.
Abstract: A recent study of CeTiGe identified this compound as a paramagnetic heavy Fermion system where the full J = 5/2 multiplet is involved in the formation of the ground state. Here we present a preliminary investigation of the dc-magnetization Mdc(H) and of the magnetoresistance Ï(H) of polycrystalline CeTiGe samples in applied magnetic fields up to Î¼0H = 14 T. The results reveal a pronounced metamagnetic transition at a critical field Î¼0Hc â‰ˆ 13.5 T at low temperatures, with a step like increase in Mdc(H) of at least 0.6 Î¼B/Ce. The metamagnetic transition leads to a strong decrease in Ï(H). A clear hysteresis in Mdc(H) and Ï(H) indicate that in CeTiGe these metamagnetic features correspond to a true thermodynamic, first order type transition in contrast to the critical behavior observed in the canonical system CeRu2Si2. Measurements at higher temperatures showed a continuous suppression of the metamagnetic transition with increasing T, which vanishes at T âˆ¼ 30 K. Â© 2010 IOP Publishing Ltd.
Deppe, M., P. Pedrazzini, N. Caroca-Canales, C. Gelbel, and J. G. Sereni. "Investigations of CePd1-xRhx single crystals located near a ferromagnetic quantum critical point." PHYSICA B-CONDENSED MATTER 378-380 (2006): 96–97.
Abstract: Investigations of CePd1-xRhx polycrystals have revealed a continuous transition from a ferromagnetic state at x = 0 to an intermediate valence state at x = 1 and evidenced non-Fermi liquid behavior near the critical concentration x(c) approximate to 0.85 where T-C is continuously suppressed to T = 0 K. We present here first results of specific heat and magnetization measurements on CePd1-xRhx single crystals with composition close to the critical point. They confirm the results obtained on polycrystals and reveal a rather low magnetic anisotropy, despite the orthorhombic structure. (c) 2006 Elsevier B.V. All rights reserved.
Hartmann, S., M. Deppe, N. Oeschler, N. Caroca-Canales, J. G. Sereni, and C. Geibel. "Ferromagnetism in CePd1-xRhx single crystals." Journal of Optoelectronics and Advanced Materials 10, no. 7 (2008): 1607–1611.
Abstract: The orthorhombic CePd1-xRhx alloy exhibits a continuous evolution from a ferromagnetic ground state at x = 0 to
intermediate-valence behavior for x = 1. Here, we report on specific heat CP(T), resistivity Ï(T) and magnetization M(T)
measurements on single crystals in a Rh concentration range 0.2 < x < 0.65 exploring the ferromagnetic side of the
magnetic phase diagram. The transport and thermodynamic properties of the ferromagnetic phase have been investigated
in the temperature range from 300 K down to 0.35 K and analyzed in terms of a gap in the magnon spectrum and an
underlying Kondo contribution. Crystal electric field parameters are deduced from specific heat measurements well above
Tc- The competition between Kondo effect and ferromagnetism has been studied in dependence of the Rh concentration in
the system. Particularly, the enhanced Sommerfeld coefficient Î³(x) indicates strong Kondo interactions when the Curie
temperature is reduced.
Kuchler, R., P. Gegenwart, J. Custers, O. Stockert, N. Caroca-Canales, C. Geibel, J. G. Sereni, and F. Steglich. "Quantum criticality in the cubic heavy-fermion system CeIn3-xSnx." Physical Review Letters 96, no. 25 (2006): 256403.
Abstract: We report a comprehensive study of CeIn3-xSnx (0.55 <= x <= 0.8) single crystals close to the antiferromagnetic quantum-critical point (QCP) at x(c)approximate to 0.67 by means of the low-temperature thermal expansion and Gruneisen parameter. This system represents the first example for a cubic heavy fermion in which T-N can be suppressed continuously down to T=0. A characteristic sign change of the Gruneisen parameter between the antiferromagnetic and paramagnetic states indicates the accumulation of entropy close to the QCP. The observed quantum-critical behavior is compatible with the predictions of the itinerant theory for three-dimensional critical spin fluctuations. This has important implications for the role of the dimensionality in heavy-fermion QCPs.
Pedrazzini, P., M. G. Berisso, N. Caroca-Canales, M. Deppe, C. Geibel, and J. G. Sereni. "Low temperature magnetic phase diagram of the cubic non-Fermi liquid system Celn(3-x)Sn(x)." The European Physical Journal B – Condensed Matter 38, no. 3 (2004): 445–450.
Abstract: In this paper we report a comprehensive study of the magnetic susceptibility (x), resistivity (p), and specific heat (C-P), down to 0.5 K of the cubic CeIn3-xSnx alloy. The ground state of this system evolves from antiferromagnetic (AF) in CeIn3 (T-N = 10.2 K) to intermediate-valent in CeSn3, and represents the first example of a Ce-lattice cubic non-Fermi liquid (NFL) system where T-N(x) can be traced down to T = 0 over more than a decade of temperature. Our results indicate that the disappearance of the AF state occurs near x(c) approximate to 0.7, although already at x approximate to 0.4 significant modifications of the magnetic ground state are observed. Between these concentrations, clear NFL signatures are observed, such as rho(T) approximate to rho(0) + A T-n (with n < 1.5) and C-P(T) proportional to -T ln(T) dependencies. Within the ordered phase a first order phase transition occurs for 0.25 < x < 0.5. With larger Sn doping, different weak rho(T) dependencies are observed at low temperatures between x = 1 and x = 3 while C-P/T shows only a weak temperature dependence.
Pedrazzini, P., M. G. Berisso, N. Caroca-Canales, M. Deppe, C. Geibel, and J. G. Sereni. "Non-Fermi liquid behaviour in cubic CeIn3-xSnx." PHYSICA B-CONDENSED MATTER 312 (2002): 406–407.
Abstract: The alloy between the antiferromagnetic (AF) CeIn3 and the mixed valent CeSn3 is particularly interesting since it is one of the few cases where a magnetic to non-magnetic transition is observed in a cubic system. Although the resulting alloy CeIn3-xSnx has been investigated for over 20 years, no information is available about thermodynamic and transport properties below 2K. We report first measurements on resistivity rho(T) and specific heat C-P(T) down to 0.45 K. These results confirm the disappearance of the AF state near xcongruent to0.6. In samples close to this critical concentration, we observe a strong departure from the Fermi liquid behaviour, i.e. rho(T) approximate to rho(0) + a T-n (n < 1.5) and a logarithmic temperature dependence C-P(T)infinity – T ln (T), in more than a decade above the lowest investigated temperature. (C) 2002 Elsevier Science B.V. All rights reserved.
Pedrazzini, P., M. G. Berisso, J. G. Sereni, N. Caroca-Canales, M. Deppe, and C. Geibel. "Complex magnetic phase diagram near the quantum critical point in CeIn3-xSnx." ACTA PHYSICA POLONICA B 34, no. 2 (2003): 363–366.
Abstract: A recent reinvestigation of the alloy system CeIn3-xSnx between the antiferromagnetic (AF) Kondo-lattice CeIn3 and the intermediate valent CeSn3 has shown that the AF order disappears at a quantum critical point (QCP) at x(c) approximate to 0.65. Preliminary evidences for a first order transition below T-N at x < x(c), indicating a complex magnetic phase diagram, have motivated the present detailed investigation of specific heat and resistivity on fine tuned samples in the 0.25 less than or equal to x less than or equal to x(c) range. These results confirm the first order transition at T-I < T-N in a reduced concentration range (0.25 < x < 0.47) and suggest that the phase boundary T-I (x) merge with the T-N(x) near x approximate to 0.37, leading to a tetracritical point. A similar first order transition was previously observed in the CeCu2(Si,Ge)(2) system at low Ge-concentration. Since in this alloy the first order transition also appears in the vicinity of a QCP, the question arises concerning how general this property is at AF critical points in Ce-based alloy systems.