J.-M. Mignot

Metamagnetic CeRu2Si2: New perspectives for heavy-fermion studies in high fields

Abstract Interesting magnetic effects have recently been reported to occur in the normal phase of heavy-fermion systems. Among them are the metamagnetic properties of UPt 3 and CeRu 2 Si 2 ( H M = 20 and 8 T). High-pressure magnetization and magnetoresistance, as well as magnetostriction measurements have been performed on CeRu 2 Si 2 . The magnetostriction data imply a remarkable scaling behavior for the magnetization as a function of P and thus a relation between H M and the characteristic Fermi-liquid energy k B T ∗ . The magnetoresistance suggests that the field enhancement of the effective mass derived from the specific-heat γ( H ) leads to the observed transition at H M for a critical value of m ∗ which is pressure independent.

Magnetic structure of CeRhIn5 as a function of pressure and temperature

We report magnetic neutron-diffraction and electrical resistivity studies on single crystals of the heavy-fermion antiferromagnet CeRhIn

High-pressure transport coefficients of the heavy-fermion superconductor CeCu2Si2

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Long-range order and low-energy magnetic excitations in CeRu2Al10 studied via neutron scattering

at pressures up to 2.3 GPa. These experiments show that the staggered moment of Ce and the incommensurate magnetic structure change weakly with applied pressure up to 1.63 GPa, where resistivity, specific heat and NQR measurements confirm the presence of bulk superconductivity. This work places new constraints on an interpretation of the relationship between antiferromagnetism and unconventional superconductivity in CeRhIn

High-field magnetostriction in the pseudo-metamagnetic heavy-fermion system CeRu2Si2

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Interaction Driven Subgap Spin Exciton in the Kondo Insulator SmB6

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Neutron diffraction study of (Ce, La)Ru2Si2 alloys in an external field

Abstract The electrical resistivity and the absolute thermoelectric power of the dense Kondo compound CeCu2Si2 were measured under very high pressures. At low temperatures, the results indicate a transition in the normal-state electronic properties around 20–30 kbar, from a strongly correlated Fermi-liquid regime (the so-called heavy-fermion state) into an IV phase. The crossover is associated with a steep increase of the critical temperature from ∼ 0.9 to ∼ 2 K. It is argued that this behavior may be due to a change from heavy-fermion to normal sd-band superconductivity.

Neutron scattering study of magnetic fluctuations in Ce1−xLaxRu2Si2(x = 0, x = 0.2)

= 27 K wasinvestigated by neutron scattering. Powder diffraction patterns show clear superstructure peakscorresponding to forbidden (h+ k)-odd reflections of the Cmcm space group. Inelastic neutronscattering experiments further reveal a pronounced magnetic excitation developing in the orderedphase at an energy of 8 meV.

Incommensurabilities and metamagnetism in the heavy-fermion alloys (Ce0.8La0.2)Ru2Si2 and CeRu2(Si0.9Ge0.1)2

Low-temperature magnetostriction experiments have been performed on CeRu2Si2 single crystals in magnetic fields up to 15T. WhenH is applied parallel to the tetragonalc-axis, a very large expansion is observed in all lattice directions. A pronounced anomaly occurs at a field close to the “metamagnetic” threshold. The results are discussed with use of thermodynamic relations and support a very simple scaling behavior for the pressure dependence of the magnetization.

Ferromagnetic Mixed-Valence and Kondo-Lattice State in TmTe at High Pressure

Using inelastic neutron scattering, we map a 14 meV coherent resonant mode in the topological Kondo insulator SmB6 and describe its relation to the low energy insulating band structure. The resonant intensity is confined to the X and R high symmetry points, repeating outside the first Brillouin zone and dispersing less than 2 meV, with a 5d-like magnetic form factor. We present a slave-boson treatment of the Anderson Hamiltonian with a third neighbor dominated hybridized band structure. This approach produces a spin exciton below the charge gap with features that are consistent with the observed neutron scattering. We find that maxima in the wave vector dependence of the inelastic neutron scattering indicate band inversion.