Heavy fermions in kondo lattices

Abstract

Electric, magnetic and thermoelectric properties of cerium solid solutions realizing the transition from Kondo impurity to Kondo lattice ((Ce,La)Al 3) and from low T K Kondo lattice to high T K Kondo lattice (Ce(Cu,Ni) 5) were studied. The anomalous low temperature properties of these compounds are related to the formation of the giant Abrikosov-Suhl resonance in the vicinity of the Fermi level. The effect of the crystal field splitting of the f level on Kondo anomalies is discussed. Resistivity and a.c. susceptibility of ferromagnetic Kondo lattice CeSi itx is studied under pressures up to 15kbar. A three-dimensional picture of the upper critical field in superconducting KL CeCu 2Si 2 is obtained. The dH c2 dT value is constant within 5% when H is rotated in the basal plane whereas d H c2dT is decreased by a factor of two when H is rotated by 5°–8° from that plane. These data are analysed within the framework of symmetry classification of possible superconducting classes in heavy fermion superconductors. The Hall coefficient R H ( T) in CeAl 3, CeCu 2Si 2 and UBe 13is measured. It has been shown that the drastic decrease in the R H ( T) value at T ⪡ T K is caused by the transition from non-coherent Kondo singlets to coherent Kondo spin fluctuations in Kondo lattices.