Magnetic Form Factor of<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>α</mml:mi></mml:math>-Ce: Towards Understanding the Magnetism of Cerium

Murani, A.P.; Levett, S. J.; Taylor, J. W.

doi:10.1103/physrevlett.95.256403

Cited by 39 publications

(44 citation statements)

References 18 publications

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“…pected [32]. This confirms that the main source of entanglement between the f local space and its environment is the hybridization between the f and the spd electrons.…”

supporting

confidence: 73%

“…4 are illustrated the averaged quasiparticle renormalization weights Z of the 7/2 and 5/2 f -electrons -which are significantly different because of the spin-orbit effect. As expected [32], the f -electrons are correlated (Z is significantly smaller than 1) even in the α phase, and the two Z's monotonically decrease by increasing the volume at higher pressures. Nevertheless, they develop a qualitatively different behaviour at the crossover point.…”

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confidence: 54%

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γ−αIsostructural Transition in Cerium

et al. 2013

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Below the critical temperature Tc ≃ 600K, an iso-structural transition, named γ-α transition, can be induced in Cerium by applying pressure. This transition is first-order, and is accompanied by a sizable volume collapse. A conclusive theoretical explanation of this intriguing phenomenon has still not been achieved, and the physical pictures proposed so far are still under debate. In this work, we illustrate zero-temperature first-principle calculations which clearly demonstrate that the γ-α transition is induced by the interplay between the electron-electron Coulomb interaction and the spin-orbit coupling. We address the still unresolved problem on the existence of a second low-T critical point, i.e., whether the energetic effects alone are sufficient or not to induce the γ-α transition at zero temperature.The γ-α iso-structural transition in Cerium [1] was discovered in 1949 [2]. Since then, a lot of theoretical and experimental work has been devoted to its understanding. The great interest in this phenomenon arises from the fact that the transition is isostructural, i.e., the lattice structure of the system is equal in the two phases. Furthermore, the possibility that the underlying mechanism lies in the electronic structure only -i.e., without it being necessary to involve other effects -makes Cerium a potential theoretical testing ground for basic concepts of correlated electron systems. Two main theoretical pictures are still under debate to explain the volume collapse: the Kondo volume collapse (KVC) [3,4] and the orbital-selective Mott transition within the Hubbard model (HM) [5]. According to the KVC the transition is induced by the rapid change of the coherence temperature across the transition boundaries, which affect dramatically the structure of the conduction spd electrons through Kondo effect. According to the HM, instead, it is the hopping between f orbitals that changes drastically across the transition between the α phase (with delocalized f electrons) and the γ phase (with localized f electrons), as for the Mott transition in the Hubbard model.Consistently with both the HM and the KVC pictures, the f -electrons are strongly correlated both in the α and in the γ phase. This fact is clearly indicated, e.g., by the photoemission spectra, which is known experimentally [6][7][8] and theoretically [9][10][11]. Despite this similarity, there is a key difference between these two models: while the KVC attributes a very important role to the interplay between the localized 4f orbitals and the itinerant spd conduction bands, the itinerant electrons are "spectators" in the HM picture.The development of LDA+DMFT (Local Density Approximation plus Dynamical Mean Field Theory) [12] results [13][14][15] has successfully reproduced many aspects of this transition, and different aspects of these studies can be understood in both physical pictures. There are still fundamental questions which have not been answered. (1) What is the role of the spin-orbit interaction (SOC) for the volume-collapse? (2) What is the ...

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“…pected [32]. This confirms that the main source of entanglement between the f local space and its environment is the hybridization between the f and the spd electrons.…”

supporting

confidence: 73%

mentioning

confidence: 54%

γ−αIsostructural Transition in Cerium

et al. 2013

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“…17 Magnetic properties at atmospheric pressure are generally consistent with atomic 4f Hund's rules moments, 4,18 while the susceptibility for the collapsed α-Ce phase 7 and for early actinide analogs 19 is temperature-independent, enhanced Pauli paramagnetic, indicating absent or screened moments. On the other hand, high energy neutron scattering measurements for Ce, 20 and x-ray emission spectroscopy for Gd, 21 continue to detect 4f moments in the collapsed phases, possibly sensing underlying "bare" moments in spite of screening effects. The 4f electron delocalization itself may be examined using resonant inelastic x-ray scattering determination of the probabilities of finding f n±1 configurations in a compressed rare earth of nominal f n character.…”

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confidence: 99%

Screening of4fmoments and delocalization in the compressed light rare earths

2009

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Spin and charge susceptibilities and the 4f n , 4f n−1 , and 4f n+1 configuration weights are calculated for compressed Ce (n = 1), Pr (n = 2), and Nd (n = 3) metals using dynamical mean field theory combined with the local-density approximation. At ambient and larger volumes these trivalent rare earths are pinned at sharp 4f n configurations, their 4f moments assume atomic-limiting values, are unscreened, and the 4f charge fluctuations are small indicating little f state density near the Fermi level. Under compresssion there is dramatic screening of the moments and an associated increase in both the 4f charge fluctuations and static charge susceptibility. These changes are coincident with growing weights of the 4f n−1 configurations, which it is argued are better measures of delocalization than the 4f n+1 weights which are compromised by an increase in the number of 4f electrons caused by rising 6s, 6p bands. This process is continuous and prolonged as a function of volume, with strikingly similarity among the three rare earths, aside from the effects moderating and shifting to smaller volumes for the heavier members. The observed α-γ collapse in Ce occurs over the large-volume half of this evolution, the Pr analog at smaller volumes, and Nd has no collapse.

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“…Above 0.8 GPa at 298 K, pure Ce metal undergoes an isostructural transition from an a face-centered cubic (fcc) phase (␥-Ce) to a denser, high-pressure, fcc phase (␣-Ce) accompanied by a 15% volume collapse. Since its discovery by P. W. Bridgman in 1927 (10), the ␥-␣ Ce transition has been the subject of extensive experimental (11,12) and theoretical investigations (7,(13)(14)(15)(16) and is often cited as an archetypal example of a localizeditinerant 4f electronic transition. Various scenarios including Mott transition (7), Kondo hybridization (8,13), and intermediate behaviors between the two (14, 15) have been proposed.…”

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confidence: 99%

Substitutional alloy of Ce and Al

Zeng

Ding

Mao

et al. 2009

Proc. Natl. Acad. Sci. U.S.A.

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The formation of substitutional alloys has been restricted to elements with similar atomic radii and electronegativity. Using high-pressure at 298 K, we synthesized a face-centered cubic disordered alloy of highly dissimilar elements (large Ce and small Al atoms) by compressing the Ce 3Al intermetallic compound >15 GPa or the Ce3Al metallic glass >25 GPa. Synchrotron X-ray diffraction, Ce L3-edge absorption spectroscopy, and ab initio calculations revealed that the pressure-induced Kondo volume collapse and 4f electron delocalization of Ce reduced the differences between Ce and Al and brought them within the Hume-Rothery (HR) limit for substitutional alloying. The alloy remained after complete release of pressure, which was also accompanied by the transformation of Ce back to its ambient 4f electron localized state and reversal of the Kondo volume collapse, resulting in a non-HR alloy at ambient conditions. 4f electron delocalization ͉ Ce-Al solid solution alloy ͉ high pressure ͉ Hume-Rothery rules ͉ metallic glass C ombining one metal with another leads to a range of alloys with properties superior to each individual end member. Since the Bronze and Iron Ages, the quest for new metallic alloys through various chemical and metastable quenching paths has played a crucial role in the advancement of civilizations. The most common type of alloy is a substitutional crystalline solid solution in which atoms of one element randomly substitute for atoms of another element in a crystal structure. The possibilities for substitution, however, are restricted by the classic empirical Hume-Rothery (HR) rules (1), which require the components have atomic size within 15% and electronegativity within 0.4 of each other. For instance, the archetypal 4f metal Ce alloys with similar rare-earth metals to form ''mischmetal,'' which has unusual pyrophoric properties and strength for a broad range of chemical and physical applications, and the sp-bonded light metal Al alloys with similar atoms to form a family of aluminum alloys that have enormous technological importance and application in everyday life. No known binary substitutional crystalline alloy exists between Ce and Al because their differences of 28% in atomic radii and 0.45 in electronegativity far exceed the HR limit. They can only form stoichiometric compounds in which Ce and Al are chemically ordered and occupy separate crystallographic sites, or metallic glass synthesized by rapidly quenched from melt in which Ce and Al are disordered both chemically and structurally. Here, we report the formation of a Ce-Al substitutional crystalline alloy from intermetallic compound and metallic glass at high pressure and room temperature, this alloy can be recovered as a non-HR alloy to ambient conditions. Pressure is a powerful tool for altering individual atoms and their electronic structures, changing the bonding chemistry, and creating novel materials (see, for example, ref. 2). This has been demonstrated by the discovery of intermetallic compounds in the incompatible K-Ni and K-Ag...

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Magnetic Form Factor ofα-Ce: Towards Understanding the Magnetism of Cerium

Cited by 39 publications

References 18 publications

γ−αIsostructural Transition in Cerium

γ−αIsostructural Transition in Cerium

Screening of4fmoments and delocalization in the compressed light rare earths

Substitutional alloy of Ce and Al

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