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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.
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.
Sereni, J. G., G. Schmerber, and J. P. Kappler. "Thermodynamic Behavior of Ce Compounds Close to a T->0 Critical Point." IEEE Transactions on Magnetics 49, no. 8 (2013): 4647–4651.
Abstract: There is a reduced group of Ce very heavy Fermions (VHF) which do not order magnetically down to at least T â‰ˆ 500 mK because they are very close to a Tord = 0 critical point. These compounds are at the top of the limTâ†’ 0 Cm/T specific heat values because they collect very high density of low energy excitations. From the analysis of Cm(T)/T and entropy Sm(T) dependencies performed on selected CePd3Mx ternaries (where M = B and Be) a quantitative evaluation of an upper limit for the density of excitations can be proposed. These observations exclude any evidence of Cm(T)/T divergency as Tâ†’ 0 in agreement with thermodynamic laws. A comparison with selected Yb-base VHF supports these features.