20 research outputs found
Critical Fields of the "Heavy-Fermion" Superconductor CeCu2Si2
FWN – Publicaties zonder aanstelling Universiteit Leide
Field-induced magnetic transitions in the quasi-two-dimensional heavy-fermion antiferromagnets Ce_{n}RhIn_{3n+2} (n=1 or 2)
We have measured the field-dependent heat capacity in the tetragonal
antiferromagnets CeRhIn and CeRhIn, both of which have an
enhanced value of the electronic specific heat coefficient
mJ/mol-Ce K above . For the specific heat data at zero
applied magnetic field are consistent with the existence of an anisotropic
spin-density wave opening a gap in the Fermi surface for CeRhIn while
CeRhIn shows behavior consistent with a simple antiferromagnetic
magnon. From these results, the magnetic structure, in a manner similar to the
crystal structure, appears more two-dimensional in CeRhIn than in
CeRhIn where only about 12% of the Fermi surface remains ungapped
relative to 92% for CeRhIn. When both compounds behave in a
manner expected for heavy fermion systems as both and the electronic
heat capacity decrease as field is applied. When the field is applied in the
tetragonal basal plane (), CeRhIn and CeRhIn have very
similar phase diagrams which contain both first- and second-order field-induced
magnetic transitions .Comment: 15 pages, 4 figure
Thermodynamic properties of the periodic Anderson model:X-boson treatment
We study the specific dependence of the periodic Anderson Model (PAM) in the
limit of employing the X-boson treatment in two fifferent regimes of
the PAM: the heavy fermion Kondo (HF-K) and the heavy fermion local magnetic
regime (HF-LMM). We obtain a multiple peak structure for the specific heat in
agreement with experimental results as well as the increase of the electronic
effective mass at low temperatures associated with the HF-K regime. The entropy
per site at low T tends to zero in the HF-K regime, corresponding to a singlet
ground state, and it tends to in the HF-LMM, corresponding to a
doublet ground state at each site. The linear coefficient
of the specific heat qualitatively agrees with the experimental results
obtained for differents materials in the two regimes considered here.Comment: 9 pages, 14 figure
Heat capacity studies of Ce and Rh site substitution in the heavy fermion antiferromagnet CeRhIn_5;: Short-range magnetic interactions and non-Fermi-liquid behavior
In heavy fermion materials superconductivity tends to appear when long range
magnetic order is suppressed by chemical doping or applying pressure. Here we
report heat capacity measurements on diluted alloyes of the heavy fermion
superconductor CeRhIn_5;. Heat capacity measurements have been performed on
CeRh_{1-y}Ir_{y}In_5; (y <= 0.10) and Ce_{1-x}La_{x}Rh_{1-y}Ir_{y}In_5; (x <=
0.50) in applied fields up to 90 kOe to study the affect of doping and magnetic
field on the magnetic ground state. The magnetic phase diagram of
CeRh_{0.9}Ir_{0.1}In_5; is consistent with the magnetic structure of CeRhIn_5;
being unchanged by Ir doping. Doping of Ir in small concentrations is shown to
slightly increase the antiferromagnetic transition temperature T_{N} (T_{N}=3.8
K in the undoped sample). La doping which causes disorder on the Ce sublattice
is shown to lower T_{N} with no long range order observed above 0.34 K for
Ce_{0.50}La_{0.50}RhIn_5;. Measurements on Ce_{0.50}La_{0.50}RhIn_5; show a
coexistence of short range magnetic order and non-Fermi-liquid behavior. This
dual nature of the Ce 4f-electrons is very similar to the observed results on
CeRhIn_5; when long range magnetic order is suppressed at high pressure.Comment: 8 pages, 9 figure
SUPERCONDUCTING PROPERTIES OF (La, Nd )Sn3ALLOYS
Des mesures de la température de transition à l'état supraconducteur Tc en fonction de la concentration en Nd et le saut de la chaleur spécifique à Tc montrent que Nd se comporte dans LaSn3 comme un ion trivalent stable dont la dégénérescence est levée par le champ cristallin. comme on n'a pas détecté d'effet de mélange, les résultats confirment l'hypothèse que la diminution initiale relativement forte de Tc ne peut être expliquée par une interaction d'échange isotropique des spins.Measurements of the superconduction transition temperature Tc vs Nd concentration and the jump of the specific heat at Tc show that Nd in LaSn3 behaves as a stable crystal-field split trivalent ion. Since no hybridization effects have been found, the results support the assumption that the relatively large initial depression of Tc cannot be explained by isotropic spin exchange interaction
Schwere Fermionen und Kohaerenz in Kondo-Gittern: Spezifische Waerme niederenergetischer Anregungen in CER-Systemen
SIGLECopy held by FIZ Karlsruhe; available from UB/TIB Hannover / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman
CRYSTAL-FIELD EFFECTS IN (La, Nd)Sn3
Des mesures de chaleur spécifique et de la résistivité électrique des alliages (La, Nd)Sn3 à l'état normal sont présentées. En accord avec des résultats récents sur les propriétés supraconductrices, nos résultat confirment l'absence de l'effet Kondo et peuvent révéler les niveaux de champ cristallin de Nd3+ dans LaSn3We report measurements of the specific heat and the electrical resistivity of (La, Nd)Sn3 alloys in the normal state. In agreement with recent results on the superconducting properties our data confirm the absence of the Kondo effect and can reveal the crystal field scheme of Nd3+ in LaSn3