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Sereni, J. G., M. Giovannini, M. Gomez Berisso, and F. Gastaldo. "Competition between ferromagnetism and frustrated antiferromagnetism in quasi 2D Ce 2.15 (Pd 1− x Ag x ) 1.95 In 0.9 alloys." Journal of Physics: Condensed Matter 28, no. 47 (2016): 475601.
Abstract: Low temperature thermal and magnetic measurements performed on ferro-magneticl (FM) alloys of composition Ce2.15(Pd1−x Ag x )1.95In0.9 are presented. Pd substitution by Ag depresses ${{T}{\text{C}}}(x)$ from 4.1 K down to 1.1 K for x  =  0.5, which is related to the increase of band electrons, with a critical concentration extrapolated to ${{x}{\text{cr}}}\approx 0.6$ . The ${{T}{\text{C}}}(x)$ decrease is accompanied by a weakening of the magnetization of the FM phase. At high temperature (T  >  30 K) the inverse magnetic susceptibility reveals the presence of robust magnetic moments ($2.56\geqslant ~{{\mu}{\text{eff}}}\geqslant 2.4$ ${{\mu}{\text{B}}}$ ), whereas the low value of the Curie–Weiss temperature ${{\theta}{P}}\approx -10$ K excludes any relevant effect from Kondo screening. The specific heat jump at ${{T}{\text{C}}}(x)$ decreases accordingly, while an anomaly emerges at a fixed temperature ${{T}^{\ast}}\approx 1$ K. This unexpected anomaly does not show any associated sign of magnetism checked by AC-susceptibility measurements. Since the total magnetic entropy (evaluated around $T={{T}{\text{C}}}(x=0)$ ) practically does not change with Ag concentration, the transference of degrees of freedom from the FM component to the non-magnetic T * anomaly is deduced. The origin of this anomaly is attributed to an arising magnetic frustration of the ground state and the consequent entropy bottleneck produced by the divergent increasing of density of excitations at low temperature.
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Romero, M. A., A. A. Aligia, J. G. Sereni, and G. Nieva. "Interpretation of experimental results on Kondo systems with crystal field." Journal of Physics: Condensed Matter 26 (2014): 025602. http://dx.doi.org/10.1088/0953-8984/26/2/025602 (accessed September 23, 2023).
Abstract: We present a simple approach to calculate the thermodynamic properties of single Kondo impurities including orbital degeneracy and crystal field effects (CFE) by extending a previous proposal by K. D. Schotte and U. Schotte [Physics Lett. A 55, 38 (1975)]. Comparison with exact solutions for the specific heat of a quartet ground state split into two doublets shows deviations below $10\%$ in absence of CFE and a quantitative agreement for moderate or large CFE. As an application, we fit the measured specific heat of the compounds CeCu$2$Ge$2$, CePd${3}$Si${0.3}$, CePdAl, CePt, Yb$2$Pd$2$Sn and YbCo$2$Zn${20}$. The agreement between theory and experiment is very good or excellent depending on the compound, except at very low temperatures due to the presence of magnetic correlations (not accounted in the model).
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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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Martinelli, A., M. Giovannini, J. G. Sereni, and C. Ritter. "Suppression of ferromagnetic order by Ag-doping: a neutron scattering investigation on Ce2(Pd1−x Ag x )2In (x  =  0.20, 0.50)." Journal of Physics: Condensed Matter 30, no. 26 (2018): 265601.
Abstract: The ground state magnetic behaviour of Ce2(Pd0.8Ag0.2)2In and Ce2(Pd0.5Ag0.5)2In, found in the ferromagnetic branch of Ce2Pd2In, has been investigated by neutron powder diffraction at low temperature. Ce2(Pd0.8Ag0.2)2In is characterized by a ferromagnetic structure with the Ce moments aligned along the c-axis and values of 0.96(2) µB. The compound retains the P4/mbm throughout the magnetic transition, although the magnetic ordering is accompanied by a significant decrease of the lattice strain along [0 0 l], suggesting a magnetostructural contribution. The magnetic behaviour of Ce2(Pd0.5Ag0.5)2In is very different; this compound exhibits an extremely reduced magnetic scattering contribution in the diffraction pattern, that can be ascribed to a different kind of ferromagnetic ordering, with extremely reduced magnetic moments (~0.1 µ
B) aligned along [0 l 0]. These results point to a competition between different types of magnetic correlations induced by Ag-substitution, giving rise to a magnetically frustrated scenario in Ce2(Pd0.5Ag0.5)2In.
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