Mesoscopic Magnetic States in Metallic Alloys with Strong Electronic Correlations: A Percolative Scenario for<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msub><mml:mi>CeNi</mml:mi><mml:mrow><mml:mn>1</mml:mn><mml:mo>−</mml:mo><mml:mi>x</mml:mi></mml:mrow></mml:msub><mml:msub><mml:mi>Cu</mml:mi><mml:mi>x</mml:mi></mml:msub></mml:math>

2009

We review here the magnetic properties of some strongly correlated electron systems and especially cerium and uranium compounds. The normal Kondo lattice model with a localized S = 1/2 spin can account for the Kondo-magnetism competition observed in cerium or ytterbium systems, while the underscreened Kondo lattice model with a localized S = 1 spin can well account for the ferromagnetism -Kondo coexistence observed in some uranium compounds such as UTe. Then, we discuss the spin glass-Kondo competition and present the resulting phase diagrams showing spin glass, Kondo and magnetically ordered phases observed in disordered heavy fermion cerium alloys such as CeNi x Cu 1−x alloys.

Section: The Kondo-spin Glass -Magnetic Order Competitionmentioning

confidence: 99%

“…In fact, the experimental phase diagram of CeNi x Cu 1−x alloys gives a percolative transition with decreasing temperature from a cluster-glass state with ferromagnetic correlations to a disordered ferromagnetic state [36,41]. Following Ref.…”

Section: The Kondo-spin Glass -Magnetic Order Competitionmentioning

confidence: 99%

Kondo Lattice and Magnetic Properties in Strongly Correlated Electron Systems

2009

“…The first studied case is the CeNi x Cu 1−x alloys [35][36][37][38][39], but recently the CeRh x Pd 1−x alloys [40,41] have been also studied and a new cluster glass state has been identified recently in these two cases. In fact, a careful experimental study of CeRh x Pd 1−x alloys shows the presence of the Kondo clusters near x = 0.8 when the ferromagnetic phase is very close to disappear [40].…”

Section: The Spin Glass-kondo-magnetic Order Competitionmentioning

confidence: 99%

“…But, very recently, these alloys have been investigated by µSR spectroscopy or small angle neutron scattering (SANS) or magnetic experiments leading to the determination of hysteresis loops [37][38][39]. The experimental results have been analyzed in terms of "cluster glass" (CG).…”

Section: The Spin Glass-kondo-magnetic Order Competitionmentioning

confidence: 99%

The Kondo Lattice Models and Magnetism for Cerium and Uranium Systems

2010

The interplay between the Kondo effect and magnetism is important in anomalous rare-earth and actinide systems and a brief review of the different Kondo lattice models is presented here. The first studied case is the classical Kondo lattice model with S = 1/2 spins for the 4f localized electrons, which describes the strong competition between the Kondo effect and magnetic ordering leading to small ordering temperatures less than roughly 10 K. The second reviewed case describes the underscreened Kondo lattice model with S = 1 spins for the 5f localized electrons, which can account for the coexistence of both the Kondo effect and the ferromagnetic order and, therefore, the large Curie temperatures observed in actinide compounds like UTe and NpNiSi2; the question of the delocalization of the 5f electrons is also discussed here. The last case describes the competition between the "spin glass" behaviour, the Kondo effect and the magnetic ordering in disordered cerium alloys like CeNixCu1−x or CeRhxPd1−x and several models used for the spin glass state are reviewed, as well as the occurrence of magnetic glass clusters.

“…However, a real improvement will be provided by trying to describe better the clusters which are yielding the cluster-glass state (CG) with ferromagnetic correlations and the IFM state and also the observed percolative CGIFM transition observed with decreasing temperature [46,47]. A rst approach had been proposed to obtain clusters with intrasite Kondo interactions and both intra-and inter-cluster magnetic interactions within the SherringtonKirkpatrick approach [58].…”

Section: (1005)mentioning

confidence: 99%

Kondo Lattice Models for Rare-Earth and Actinide Systems

2012

We present here some works on the strong competition between the Kondo eect, magnetic order and eventually spin glass or frustration eect in anomalous rare-earth and actinide systems. First, we develop an underscreened Kondo lattice model with S f = 1 spins for the 5f -electrons and we have recently improved it by deriving, by the SchrieerWol transformation, a 5f -band with a nite bandwidth. The underscreened Kondo lattice model can account for properties of some uranium and neptunium compounds, like UTe, Np2PdGa3 or UCu2Si2 which have a large Curie temperature Tc of order 100 K and present also a Kondo behavior. In particular, we can account for the observed maximum of Tc under pressure in UTe and the magnetization curves of NpNiSi2 showing the occurrence of the Kondo eect at low temperatures below Tc. Second, we have studied the properties of disordered cerium alloys like CeCuxNi1−x or CeRhxPd1−x by considering the Kondo eect, a ferromagnetic order and a spin glass behavior described by several approaches. The van Hemmen approach gives a good explanation of the properties of cerium alloys and we are describing the magnetic glass clusters which occur in both spin glass and ferromagnetic phases. Third, we present a new description of a frustrated Kondo lattice model, which can account for the behavior under pressure or doping of some ytterbium compounds like Yb2Pd2Sn and YbAgGe.