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ÄŒurlík, I., M. Giovannini, F. Gastaldo, A. M. Strydom, M. Reiffers, and J. G. Sereni. "Crystal structure and physical properties of the two stannides EuPdSn2 and YbPdSn2." Journal of Physics: Condensed Matter 30, no. 49 (2018): 495802.
Abstract: We report on synthesis, crystal structure and physical properties of the isotypic compounds YbPdSn2 and EuPdSn2 crystallizing in the MgCuAl2-type structure. In both stannides a divalent state of respective rare earth element was found from analysis of the magnetic susceptibilities. Whereas in YbPdSn2 only weak paramagnetic behaviour is observed, in EuPdSn2 a long-range magnetic phase transition occurs at 12.5 K with complex magnetic behaviour evidenced by magnetic susceptibity and specific heat measurements. Under the influence of magnetic field, the magnetic behaviour was found to evolve from an antiferromagnetic to a ferromagnetic state as a consequence of a re-arrangement of magnetic moments.
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Banda, J., D. Hafner, J. F. Landaeta, E. Hassinger, K. Mitsumoto, M. Giovannini, J. G. Sereni, C. Geibel, and M. Brando. Electronuclear Quantum Criticality., 2023.
Abstract: We present here a rare example of electronuclear quantum criticality in a metal. The compound YbCu4.6Au0.4 is located at an unconventional quantum critical point (QCP). In this material the relevant Kondo and RKKY exchange interactions are very weak, of the order of 1 K. Furthermore, there is strong competition between antiferromagnetic and ferromagnetic correlations, possibly due to geometrical frustration within the fcc Yb sublattice. This causes strong spin fluctuations which prevent the system to order magnetically. Because of the very low Kondo temperature the Yb3+ 4f-electrons couple weakly with the conduction electrons allowing the coupling to the nuclear moments of the 171Yb and 173Yb isotopes to become important. Thus, the quantum critical fluctuations observed at the QCP do not originate from purely electronic states but from entangled electronuclear states. This is evidenced by the anomalous temperature and field dependence of the specific heat at low temperatures.
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Bauer, E., A. Galatanu, P. Rogl, M. G. Berisso, P. Pedrazzini, and J. G. Sereni. "Loss of magnetism in CePd2-xNixAl3." PHYSICA B-CONDENSED MATTER 312 (2002): 464–465.
Abstract: Hexagonal CePd2-xNixAl3 exhibits a crossover from a Kondo lattice showing magnetic order at T(N)similar or equal to2.8 K for xless than or equal to0.2 to intermediate valence (IV) for x-->2. Though T-N(x) is weakly affected upon Pd/Ni substitution before vanishing at finite temperature, the Kondo temperature T-K progressively increases. Above xsimilar or equal to0.3 the phase boundary no longer exists and strong spin fluctuations cause pronounced deviations from a Fermi-liquid ground state before the IV regime is established for xgreater than or equal to1. (C) 2002 Elsevier Science B.V. All rights reserved.
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Bauer, E., R. Hauser, A. Galatanu, A. Lindbaum, G. Hilscher, H. Sassik, H. Kirchmayr, J. G. Sereni, and P. Rogl. "New phase boundary between magnetic and non-Fermi-liquid in Ce(Rh1-xRux)(3)B-2, for 0 <= x <= 0.4." Journal of Applied Physics 83, no. 11 (1998): 6423–6425.
Abstract: A study of the temperature-dependent magnetic susceptibility and electrical resistivity rho(T) (0.5-300 K) on single-phase alloys (CaCu5 type), prepared by argon are melting, reveals a magnetic phase transition with a nonmonotonous decrease of the ordering temperature from T-c = 115 K for x = 0 to T-c approximate to 0 for x = 0.40. A kink in the susceptibility at about 70 K indicates that ferromagnetism (at x < 0.1) transforms to a complex magnetic order for 0.125 less than or equal to x less than or equal to 0.35. Above that concentration rho(T) = rho(0) + AT(n) changes from n approximate to 2 to n approximate to 1.5, a characteristic for non-Fermi-liquid behavior. Under pressure T-c stays almost constant for x = 0.125 but dT(c)/dp grows with increasing Ru content. On the contrary, applied fields up to 12 T do not affect T-c. Low-temperature specific heat and ac susceptibility for x = 0.40 confirm the absence of long-range magnetic order down to 0.5 K, For x = 0.35 C-p/T = 62 mJ/mol K at 1.5 K, a value which is three times larger than that of CeRh3B2. (C) 1998 American Insitute of Physics. [S0021-8979(98)46511-3].
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Bauer, E., R. Hauser, E. Gratz, D. Gignoux, D. Schmitt, and J. G. Sereni. "Transport and thermodynamical properties of Yb(Cu,Al)5 compounds." Journal of Physics: Condensed Matter 4, no. 18 (1992): 7829.
Abstract: Substitutions for Cu with Al in YbCu5 stabilize the hexagonal CaCu5 structure and cause a crossover from a divalent behaviour of the Yb ion in YbCu5 to a stable integer 3+ behaviour of Yb in YbCu3Al2. Additionally, this substitution is responsible for the appearance of long-range magnetic order of a certain antiferromagnetic type in the compound YbCu3Al2 below 1.9 K.
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Bauer, E., R. Hauser, L. Keller, P. Fischer, O. Trovarelli, J. G. Sereni, J. J. Rieger, and G. R. Stewart. "Onset of magnetic order in YbCu5-xAlx." Physical Review B 56, no. 2 (1997): 711–718.
Abstract: Spectroscopic, magnetic, thermal, and transport measurements under pressure are presented which were performed on YbCu5-xAlx intermetallics. The substitution of Cu by Al in YbCu5 drives the system from an almost divalent behavior of the Yb ion in YbCu5 to a trivalent state in YbCu3Al2. A compensation between the normal thermal expansion and a valence-driven contraction was found for YbCu4Al. Antiferromagnetic order sets in for x>1.5, where an increasing Al content causes both a growing transition temperature and rising saturation moments reaching 2 K and about 2.1 mu(B), respectively, for x=2. At the critical concentration (x approximate to 1.5) the possibility of a non-Fermi-liquid state is analyzed together with its tuning by pressure.
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Bauer, E., R. Hauser, H. Michor, G. Hilscher, A. Galatanu, M. Galli, J. G. Sereni, and P. Bonville. "Evolution of a non-Fermi-liquid state in YbCu5-xAlx." Physica B 259-261 (1999): 426–428.
Abstract: The growing valency of the Yb ion, when Cu is substituted by Al in YbCu5 – xAlx, causes a magnetic instability at a critical concentration x(cr) approximate to 1.5. Alloys in the vicinity of x(cr) exhibit typical non-Fermi-liquid properties. (C) 1999 Elsevier Science B.V. All rights reserved.
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Bauer, E., G. Hilscher, H. Michor, Ch. Paul, Y. Aoki, H. Sato, D. T. Adroja, J. - G. Park, P. Bonville, C. Godart et al. "The magnetic instability of Yb2Pd2(In,Sn) in a non-Fermi liquid environment." Journal of Physics: Condensed Matter 17 (2005): S999–S1009.
Abstract: Various concentrations of the solid solution Yb2 Pd2 In1−x Sn x ranging from
x = 0 to 1 with the tetragonal Mo2 FeB2 -type structure were prepared and
their physical properties were studied by means of bulk and spectroscopic
measurements as a function of temperature, pressure and magnetic fields.
Results deduced from these studies indicate a slight variation of the valency of
the Yb ions, from ν ≈ 2.9 for both border compounds to ν = 3 at x = 0.6. This
variation gives rise to the appearance of long range magnetic order in a narrow
concentration region around x = 0.6, while both border compounds remain
non-magnetic. The outstanding concentration dependence for the ordered
regime may be indicative of two quantum critical points, a novel feature not yet
observed in Yb compounds.
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Bauer, E., H. Kaldarar, A. Prokofiev, E. Royanian, A. Amato, J. G. Sereni, W. Bramer-Escamilla, and I. Bonalde. "Heavy Fermion Superconductivity and Antiferromagnetic Ordering in CePt3Si without Inversion Symmetry." Journal of the Physical Society of Japan 76, no. 5 (2007): 051009.
Abstract: Heavy fermion superconductivity in absence of inversion symmetry of the crystal structure is basically controlled by a Rashba-like antisymmetric spin orbit coupling which splits the Fermi surface and removes the spin degeneracy of electrons. The Fermi surface splitting originates a mixing of spin-singlet and spin-triplet states in the superconducting condensate. Such constraints are responsible for various uncommon features of the superconducting ground state and are discussed here in view of CePt 3 Si, the first heavy fermion superconductor missing a centre of symmetry. We recall and discuss normal and superconducting properties of CePt 3 Si and relate them to recently developed phenomenological theories.
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Berger, S., A. Galatanu, G. Hilscher, H. Michor, C. Paul, E. Bauer, P. Rogl, M. Gomez-Berisso, P. Pedrazzini, J. G. Sereni et al. "Experimental study of physical properties in the complex magnetic phase diagram of Ce(Rh1-xRux)(3)B-2." Physical Review B 64, no. 13 (2001): 134404.
Abstract: We report on a series of structural, magnetic, and thermodynamic measurements, a study of transport properties and x-ray absorption edge spectroscopy on Ce(Rh1-xRux)(3)B-2. These investigations evidence that in addition to the already established ferromagnetic range for x less than or equal to0.06, a complex antiferromagnetic structure exists for concentrations 0.1 less than or equal tox less than or equal to0.35. The behavior in the latter regime is dominated by an extraordinary strong intersite coupling; however, the magnetic moments involved appear to be very small. At the phase boundary to the paramagnetic regime (x approximate to0.4), significant deviations from a Fermi-liquid behavior occur.
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