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Sereni, J.G.; Gómez Berisso, M.; Schmerber, G.; Kappler, J.P. |
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Suppression of the Shastry-Sutherland phase in Ce2 Pd 2 Sn at a field-induced critical point |
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2010 |
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Physical Review B – Condensed Matter and Materials Physics |
Abbreviated Journal |
Phys. Rev. B Condens. Matter Mater. Phys. |
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81 |
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18 |
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184429 |
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The magnetic phase diagram of Ce2 Pd2 Sn is investigated through the field dependence of thermal, transport, and magnetic properties at low temperature. The upper transition, TM =4.8 K is slightly affected by magnetic field up to B=1 T whereas the lower one T C (B) rapidly increases from 2.1 K joining TM in a critical point at Tcr = (4.1±0.2) K for Bcr = (0.11±0.01) T. At that point, the intermediate phase, previously described as an unstable Shastry-Sutherland lattice, is suppressed. A detailed analysis around the critical point reveals a structure in the maximum of the ∂ M/∂ B (B) derivative, which may be related to a step in magnetization predicted by theory for the mentioned lattice. © 2010 The American Physical Society. |
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10980121 (ISSN) |
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BT @ berisso @ |
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595 |
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Sereni, J.G.; Schmerber, G.; Berisso, M.G.; Chevalier, B.; Kappler, J.P. |
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Title |
Tricritical point and suppression of the Shastry-Sutherland phase in Ce2(Pd1−xNix)2Sn |
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Journal Article |
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2012 |
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Physical Review B – Condensed Matter and Materials Physics |
Abbreviated Journal |
Phys. Rev. B |
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85 |
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13 |
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134404 |
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Structural, magnetization, and heat capacity measurements were performed on Ce2(Pd1−xNix)2Sn compounds covering the full range of the Mo2FeB2 structure stability (0⩽x⩽0.25). In this system, the two transitions observed in Ce2Pd2Sn (antiferromagnetic TN=4.8 K and ferromagnetic TC=2.1 K) converge into a tricritical point at Tcr≈3.4 K for xcr≈0.3, where the intermediate antiferromagnetic (AF) phase is suppressed. The decrease of the TN(x) phase boundary is due to an incipient Kondo screening of the Ce-4f moments. This effect and the increase of local atomic disorder affect the formation of Ce-magnetic dimers on which the Shastry-Sutherland lattice (SSL) builds up. On the contrary, the TC(x) transition to the ferromagnetic ground state increases as a consequence of the weakening of the intermediate phase. Applied magnetic fields also suppress the AF-SSL phase as it was already observed in the stoichiometric compound. |
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American Physical Society |
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BT @ berisso @ 10.1103/PhysRevB.85.134404 |
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639 |
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Sereni, J.G.; Gomez Berisso, M.; Braghta, A.; Schmerber, G.; Kappler, J.P. |
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Title |
Unstable Shastry-Sutherland phase in Ce2Pd2Sn |
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Journal Article |
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2008 |
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Physical Review B – Condensed Matter and Materials Physics |
Abbreviated Journal |
Phys. Rev. B |
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80 |
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2 |
Pages |
022428 |
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cerium alloys; crystal field interactions; entropy; ferromagnetic materials; frustration; magnetic anisotropy; magnetic hysteresis: magnetic transitions; palladium alloys; tin alloys |
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Thermal (CP) , magnetic ( M and χac ), and transport (Ï) measurements on Ce2Pd2Sn are reported. High-temperature properties are well described by the presence of two excited crystal-field levels at (65±5)K and (230±20)K , with negligible hybridization (Kondo) effects. According to literature, two transitions were observed at TM=4.8K and TC=2.1K , respectively. The upper transition cannot be considered as a standard antiferromagnetic because of frustration effects in a triangular network of Ce atoms and the positive sign of the paramagnetic temperature θPLT=4.4K . The nature of the intermediated phase is described accounting for the formation of ferromagnetic (F) Ce dimers disposed in a quasi-two-dimensional square lattice, resembling a Shastry-Sutherland pattern. According to hysteretic features in Ï(T) and χac(T) , the lower F transition is of first order, with CP(T<TC) revealing a gap of anisotropy Eg≈7K . |
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BT @ pedrazp @ |
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563 |
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TROVARELLI, O.; SERENI, J.G.; SCHMERBER, G.; KAPPLER, J.P. |
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Title |
Low-temperature magnetic and thermal properties of CePdSb |
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Journal Article |
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Year |
1994 |
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Physical Review B – Condensed Matter and Materials Physics |
Abbreviated Journal |
Phys. Rev. B |
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49 |
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21 |
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15179-15183 |
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Low-temperature ac and dc magnetic susceptibility, high-field magnetization, and specific-heat measurements have been carried out on CePdSb. The magnetic measurements confirm the ferromagnetic transition at T(C) = 17 K as previously reported. However, no anomaly in the specific heat is observed at that temperature, but only the onset of the magnetic contribution, C(M)(T). The maximum of C(M)(T) is observed at T(max) = 9.7 K. The lack of a C(M)(T) jump at T(C) is discussed in terms of the comparison of the exchange integrals between first- and second-nearest magnetic neighbors. Depending on their relative values, the magnetic structure can behave as low dimensional or incommensurate. The entropy of the magnetic phase (Rln2) and the low density of states (gamma = 11 mJ/mol K2) excludes a Kondo-lattice character for this compound. |
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0163-1829 |
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ISI:A1994NR42500043 |
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BT @ hernan @ |
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106 |
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Sereni, J.G.; Trovarelli, O.; Schmerber, G.; Kappler, J.P. |
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Title |
Comparative study of thermal and magnetic properties of CeTyX4-y ferromagnets |
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Journal Article |
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1997 |
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Physical Review B – Condensed Matter and Materials Physics |
Abbreviated Journal |
Phys. Rev. B |
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56 |
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9 |
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5380-5386 |
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Low-temperature thermal (specific heat, C-P) and magnetic [ac susceptibility, chi(ac), and isothermal magnetization M(B)] measurements on CeTyX4-y ferromagnets (with T = Ni, Cu, Pd, Ag, Au, and X = Ga, Al, with 0.3 < y < 0.7) are reported. With the exception of T = Ni, all compounds with X = Ga show a typical second-order ferromagnetic transition. In the case of T = Ni, magnetic correlations set in at T approximate to 3T(C), (T-C being the Curie temperature) and the C-P(T) and chi(ac)(T) maxima (at 3.3 and 4.2 K, respectively) do not coincide, while the M(B) curves reveal an antiferromagnetic character at lower temperatures. In these systems, the magnetic entropy of the ordered phase is larger than 85% of Rln2, in coincidence with the low values of the Sommerfeld coefficient gamma less than or equal to 10 mJ/mol K-2. For T = Ag and X = Al, a strong diamagnetic signal was observed at T-s = 0.63 K in chi(ac)(T), with the characteristics of a superconducting component. The thermodynamical properties of these compounds confirm the lack of hybridization when the Ce atom is in a ferromagnetic ground state. |
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0163-1829 |
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ISI:A1997XW94200062 |
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BT @ hernan @ |
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89 |
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Sereni, J.G.; Schmerber, G.; Kappler, J.P. |
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Title |
Thermodynamic Behavior of Ce Compounds Close to a T->0 Critical Point |
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2013 |
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IEEE Transactions on Magnetics |
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IEEE Trans. Magn. |
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49 |
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8 |
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4647-4651 |
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Keywords |
cerium compounds; critical points; entropy; palladium compounds; specific heat; CePd3Bx; CePd3Bex; cerium compounds; critical point; entropy; specific heat; thermodynamic behavior; Compounds; Entropy; Heating; Saturation magnetization; Temperature dependence; Temperature measurement; Thermodynamics; Cerium; magnetic properties; thermodynamics |
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There is a reduced group of Ce very heavy Fermions (VHF) which do not order magnetically down to at least T ≈ 500 mK because they are very close to a Tord = 0 critical point. These compounds are at the top of the limT→ 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 T→ 0 in agreement with thermodynamic laws. A comparison with selected Yb-base VHF supports these features. |
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0018-9464 |
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BT @ pedrazp @ |
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664 |
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Gomez Berisso, M.; Sereni, J.G.; Braghta, A.; Schmerber, G.; Chevalier, B.; Kappler, J.P. |
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Title |
Field suppression of the modulated phase of Ce2Pd2Sn |
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Journal Article |
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2009 |
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Physica B |
Abbreviated Journal |
Proceedings of the International Conference on Strongly Correlated Electron Systems |
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404 |
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19 |
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2930-2933 |
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Magnetic phases; Critical points; Ce2Pd2Sn; Ferromagnetism |
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Low temperature magnetic (M) and thermal (CP) properties of the intermetallic compound Ce2Pd2Sn have been investigated at zero and different magnetic fields. Two transitions were recognized at and , with latter nearly coinciding with the extrapolated Curie-Weiss temperature . The Curie factor evaluated from T>=TM, is [approximate]2μB. The positive value of θP, the triangular coordination of the magnetic (Ce) atoms and the weak effect of applied magnetic field, reveal that TM cannot be considered as a canonic antiferromagnetic transition like claimed in the literature. M(T) measurements under moderate magnetic fields () show TC(B) increasing while TM(B) is practically not affected. Both transition merge in a critical point at for , where the intermediate phase is suppressed. At , the cusp of a first order transition is observed in CP(T). According to the proposed ferromagnetic ground state, it is followed by a CP(T)[is proportional to]T3/2exp(-Eg/T) dependence, with a gap of anisotropy . |
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0921-4526 |
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BT @ pedrazp @ |
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562 |
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Sereni, J.G.; Trovarelli, O.; Schaf, J.; Schmerber, G.; Kappler, J.P. |
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Title |
Extremely Low Density of States in CePd7 |
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1991 |
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Modern Physics Letters B |
Abbreviated Journal |
Mod. Phys. Lett. B |
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5 |
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18 |
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1249-1253 |
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The low temperature specific heat and magnetic susceptibility measurements, up to room temperature, on CePd7 are reported. The Sommefeld coefficient gamma and the Pauli susceptibility chio were found to have the lowest values within the Ce compounds: gamma = 9.8 mJ/mole K2 and chio = 0.14 × 10-3 emu/mole. The ratio chio/gamma = 0.014 emu K2/J is that of a free electron, instead of an intermediate valence system (0.036 emu K2/J). Such a value suggests complete delocalization of the Ce 4f electrons. |
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BT @ pedrazp @ |
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684 |
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Sereni, J.G.; Nieva, G.L.; Schmerber, G.; Kappler, J.P. |
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Title |
EVIDENCES FOR UNCONVENTIONAL SUPERCONDUCTIVITY IN RARE-EARTH INTERMETALLICS |
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1989 |
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Modern Physics Letters B |
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Mod. Phys. Lett. B |
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3 |
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16 |
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1225-1231 |
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The specific heat of CeRu2 and La5Rh4 of the superconducting state does not follow a BCS-exponential temperature dependence, but a T2 law. At very low temperature (T = 0.1 Tc), CeRu2 shows a linear T dependence, which corresponds to a constant density of states. The experimental results are well described by the theoretical predictions for an axial state (CeRu2) and polar state (La5Rh4) superconductors. The small Sommerfeld coefficient of La5Rh4(? = 3.4 mJ/K2 La at.) excludes this compound from the heavy fermion superconductors. |
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BT @ gnieva @ |
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428 |
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TROVARELLI, O.; SERENI, J.G.; SCHMERBER, G.; KAPPLER, J.P. |
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Title |
COEXISTENCE OF KONDO AND SPIN-GLASS BEHAVIOR IN CE4Y3NI3 |
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1995 |
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JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS |
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140 |
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1211-1212 |
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Magnetic susceptibility chi and specific heat C-p measurements on Ce4Y3Ni3 are presented. The temperature of the maximum of chi(ac)(T) and C-p(T) shifts with frequency and applied field respectively, as expected for a spin glass (SG) system. The C-p (T --> 0) dependence corresponds to that of an anisotropic SG. According to the entropy gain two Ce atoms are involved in the SG contribution and two exhibit Kondo effect. |
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0304-8853 |
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ISI:A1995QM07400233 |
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BT @ hernan @ |
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