Magnetic susceptibility of CeRu3Si2 and a scaling effect in mixed-valence compounds (original) (raw)
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Magnetic instabilities in CeRu2Si2 compounds
Physica B: Condensed Matter, 1999
Neutron scattering experiments were recently performed in compounds of the CeRu Si family. The topic addressed is the proximity of magnetic instabilities. The first one is the proximity of a ¹"0 K quantum phase transition experimentally achieved with lanthanum doping. The second kind of instability is linked to the competition between antiferromagnetic and ferromagnetic interactions in these materials. The pseudo-metamagnetic transition of CeRu Si and the occurrence of an antiferromagnetic phase in the ferromagnetic compound CeRu Ge were studied. Comparisons with macroscopic measurements are made using a simple analysis of the data.
Magnetoresistivity anisotropy in CeRu2Si2 and derived alloys
Physica B: Condensed Matter, 1997
Magnetoresistance measurements of CeRu:Si2 single crystals performed for the field B parallel to the tetragonal c-axis and the electrical current along c or in the basal plane are reported. The thermal variation of the field B* where a sharp maximum associated with the metamagnetic-like transition occurs is quite different in the two cases. These variations are compared with those derived from other properties. Results obtained for La and Y doped alloys are also discussed.
The low-temperature magnetism of cerium atoms in CeMn2Si2 and CeMn2Ge2 compounds
Journal of Physics: …, 2004
The low-temperature magnetic properties of the Ce atoms in the intermetallic compounds CeMn 2 Ge 2 and CeMn 2 Si 2 were studied. Previous neutron scattering measurements did not detect an ordered moment at Ce atoms in either compound despite the fact that they are surrounded by the Mn moments ordered ferromagnetically in the CeMn 2 Ge 2 and antiferromagnetically in the CeMn 2 Si 2 . Contrasting with this result, a recent measurement performed with the time differential perturbed angular correlation (TDPAC) technique showed the presence of a pronounced magnetic hyperfine field (MHF) at Ce sites in the CeMn 2 Ge 2 compound and no MHF in CeMn 2 Si 2 . The absence of the Ce magnetic moment and MHF in the silicide can be understood in terms of too weak a Ce-Ce magnetic interaction while in the germanide the TDPAC result suggests that some magnetic ordering of Ce atoms may occur. Aiming to understand the effects which result in the quenching of the Ce 4f moment in both cases, we performed first-principles band-structure calculations for both systems, using the full potential linear augmented plane wave method. It is shown that the magnetism of the Ce sublattice has fundamentally different nature in CeMn 2 Si 2 and CeMn 2 Ge 2 . While the Ce atoms are intrinsically nonmagnetic in the silicide, having a zero magnetic moment with both spin and orbital contributions identically zero, they display magnetic properties in the CeMn 2 Ge 2 since their very small total moment is composed of finite spin and orbital components which almost cancel each other accidentally.
Physical Review B, 2003
The magnetic properties of CeRu2Si2 at microkelvin temperatures (down to 170 µK) and ultra small magnetic fields (0.02 ∼ 6.21 mT) are investigated experimentally for the first time. The simultaneously measured ac susceptibility and static magnetization show neither evidence of the magnetic ordering, superconductivity down to the lowest temperatures nor conventional Landau Fermi-Liquid behavior. The results imply the magnetic transition temperature in undoped CeRu2Si2 is very close to absolute 0 K. The possibility for proximity of CeRu2Si2 to the quantum critical point without any doping is discussed.
Magnetovolume study of the metamagnetic transition of CeRu2Si2 below 1 K
Physica B: Condensed Matter, 1991
We report magnetostriction and thermal-expansion measurements on a single-crystalline sample of the heavy-fermion compound CeRu,Si, in the temperature interval 0.1 < T < 1.3 K and in fields along the tetragonal axis up to 12 T, in order to study the metamagnetic-like transition. The width of the field-induced transition (at -7.7T) as observed by magnetostriction narrows on cooling and seems to remain finite at T = 0 K indicating that the transition remains continuous for the present sample.
Dynamic magnetic response in intermediate-valence CeNi
Physical Review B, 2000
The paramagnetic spectral response of the intermediate-valence compound CeNi has been studied by inelastic neutron scattering on isotopically (60 Ni) enriched single-crystal and powder samples. At low temperature (Tϳ10 K), no magnetic intensity was found up to an energy EϷ15 meV, indicating a spin-gap-like response. The absence of detectable quasielastic scattering in high-resolution time-of-flight spectra provides clear evidence for the formation of a singlet ground state due to electron correlations. The magnetic response measured at Tϭ11 K on the single crystal consists of ͑i͒ a broad structureless contribution, extending beyond 60 meV, which is a characteristic feature of valence-fluctuating materials, and ͑ii͒ two extra narrow peaks at about 18 and 34 meV, which exist for practically all Q vectors investigated, and whose intensities vary as a function of both the reduced q vector and the direction in reciprocal space. This behavior is quite unusual among intermetallic intermediate-valence compounds. It implies that the mixed-valence state in CeNi cannot be described by a single-ion Anderson model, and that magnetic correlations should be taken into account. The extra peaks are tentatively related to crystal-field interactions, which are of the same order of magnitude here as the Kondo temperature.
Magnetic form factor in CeRu2Si2 on crossing its metamagnetic transition
The magnetic form factor of the heavy fermion compound CeRu2Si2 was measured by polarized neutron diffraction in the Pauli paramagnetic phase and above the metamagnetic transition. The magnetization density is characteristic of 4f electrons in both phases with an almost pure |5/2,5/2⟩ ground-state wavefunction. The only field effect observed in this experiment corresponds to a nonlinear variation of the magnetization of the 4f electrons.
Magnetic behavior and local electronic structure of Ce2Ni3Si5 and CeNi4B
Physica B: Condensed Matter, 1999
We report on the results of magnetic susceptibility (2-300 K) and X-ray absorption near-edge structure (XANES) studies of the two polycrystalline compounds Ce Ni Si and CeNi B. XANES spectra at the Ce-M '44 threshold exhibit the signature of mixed valence behavior of Ce in both compounds, with a larger 4f occupancy in Ce Ni Si in agreement with the magnetic results. NiL ''''' XANES spectra of the two compounds reveal a 3d configuration of Ni in the ground state of both compounds. The 3d band, however, is more strongly delocalized in Ce Ni Si .
Itinerant metamagnetism of CeRu2Si2: bringing out the dead. Comparison with the new Sr3Ru2O7 case
Physica B: Condensed Matter, 2002
Focus is given on the macroscopic and microscopic experimental works realized during a decade on the clear case of itinerant metamagnetism in the heavy fermion paramagnetic compound CeRu 2 Si 2. Emphasis is made on the feedback between the band structure, the exchange coupling and the lattice instability. Sweeps in magnetic field, pressure and temperature feel the pseudogap of this strongly correlated electronic system as well as its equivalent CeRu 2 Ge 2 at a fictitious negative pressure. Some mysteries persist as the complete observation of the FS above the metamagnetic field H M and the detection of the dynamical ferromagnetic fluctuation near H M. The novelty of the bilayer ruthenate Sr 3 Ru 2 O 7 is discussed by comparison. Despite differences in spin and electronic dimensionality many common trends emerge.
Valence fluctuation in CeMo2Si2C
Journal of Alloys and Compounds, 2013
We report on the valence fluctuation of Ce in CeMo 2 Si 2 C as studied by means of magnetic susceptibility χ(T ), specific heat C(T ), electrical resistivity ρ(T ) and x-ray absorption spectroscopy. Powder x-ray diffraction revealed that CeMo 2 Si 2 C crystallizes in CeCr 2 Si 2 C-type layered tetragonal crystal structure (space group P4/mmm). The unit cell volume of CeMo 2 Si 2 C deviates from the expected lanthanide contraction, indicating non-trivalent state of Ce ions in this compound. The observed weak temperature dependence of the magnetic susceptibility and its low value indicate that Ce ions are in valence fluctuating state. The formal L III Ce valence in CeMo 2 Si 2 C < ν> = 3.11 as determined from x-ray absorption spectroscopy measurement is well bellow the value < ν>≃ 3.4 in tetravalent Ce compound CeO 2 . The temperature dependence of specific heat does not show any anomaly down to 1.8 K which rules out any magnetic ordering in the system. The Sommerfeld coefficient obtained from the specific heat data is γ = 23.4 mJ/mol K 2 . The electrical resistivity follows the T 2 behavior in the low temperature range below 35 K confirming a Fermi liquid behavior. Accordingly both the Kadowaki Wood ratio A/γ 2 and the Sommerfeld Wilson ratio χ(0)/γ are in the range expected for Fermi-liquid systems. In order to get some information on the electronic states, we calculated the band structure within the density functional theory, eventhough this approach is not able to treat 4f electrons accurately. The non-f electron states crossing the Fermi level have mostly Mo 4d character. They provide the states with which the 4f sates are strongly hybridized, leading to the intermediate valent state.