Divalent-to-trivalent transition of Sm in<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mi>SmS</mml:mi></mml:mrow></mml:math>: Implications for the high-pressure magnetically ordered state

Annese, E.; Barla, A.; Dallera, C.; Lapertot, G.; Sanchez, J.P.; Vankó, György

doi:10.1103/physrevb.73.140409

Cited by 33 publications

(36 citation statements)

References 22 publications

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“…As seen from Fig. 1(a), ν estimated from high-T experiments shows a continuous evolution with P [10][11][12]. A similar smooth P -variation is observed in the conductivity σ measured at T = 150 K [ Fig.…”

Section: +supporting

confidence: 67%

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Discontinuous Transition from a Real Bound State to Virtual Bound State in a Mixed-Valence State of SmS

et al. 2011

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Golden SmS is a paramagnetic, mixed-valence system with a pseudogap. With increasing pressure across a critical pressure Pc, the system undergoes a discontinuous transition into a metallic, antiferromagnetically ordered state. By using a combination of thermodynamic, transport, and magnetic measurements, we show that the pseudogap results from the formation of a local bound state with spin singlet. We further argue that the transition Pc is regarded as a transition from an insulating electron-hole gas to a Kondo metal, i.e., from a spatially bound state to a Kondo virtually bound state between 4f and conduction electrons.PACS numbers: 65.40. De, 71.27.+a, 75.30 -6], which are ascribed to the interplay between 4f and conduction electrons. In these mixedvalence compounds, Coulomb repulsion between 4f electrons gives rise to a gap formation on the order 10 meV at the Fermi level. While such materials behave like a Kondo metal at temperatures (T ) higher than the gap energy, they show insulating behavior at low T . For SmB 6 , the collapse of the insulating gap and the emergence of a magnetic order occur at the same pressure [7,8], which suggests that the gap formation competes with the longrange magnetic ordering.Nonalloyed SmS undergoes a phase transition under pressure (P ). With increasing P , the system undergoes a valence transition at a critical pressure of approximately P = 0.7 GPa at T = 300 K from divalence to mixed valence, accompanied by a color change from black to golden yellow [9]. In this mixed-valence phase (named golden SmS), two configurations of 4f 6 and 4f 5 are energetically degenerate:This is also described formally as (1 − ǫ) Sm 2+ + ǫ Sm 3+with 0 ≤ ǫ ≤1, which leads to the definition of the mean valence as ν = 2(1 − ǫ) + 3ǫ. Note that the Sm 2+ ion has no magnetic moment owing to the vanishment of total angular momentum. As seen from Fig. 1(a), ν estimated from high-T experiments shows a continuous evolution with P [10-12]. A similar smooth P -variation is observed in the conductivity σ measured at T = 150 K [ Fig. 1(b)]. From these results, it is inferred that the number of electrons e on the right-hand side of eq. (1) monotonically * Present address: UVSOR Facility, Institute for Molecular Science, Okazaki 444-8585, Japan.E-mail address: imura@ims@ac.jp † E-mail address: kensho@cc.nagoya-u.ac.jp increases with P . As seen from the phase diagram of Fig. 1(c), there is no phase transition as a function of P at high T .At low T , by contrast, a magnetic transition occurs at P c ∼ 1.8 GPa [13,14]. Magnetic susceptibility revealed that the ground state at P > P c is antiferromagnetic

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Section: +supporting

confidence: 67%

“…Continuous pressure evolution of (a) mean valence ν at high temperature [10][11][12] and (b) conductivity ratio σ(P )/σ(P = 0.6 GPa) at 150 K. For the definition of ν, see text. (c) P -T phase diagram of golden SmS.…”

Section: +mentioning

confidence: 99%

Discontinuous Transition from a Real Bound State to Virtual Bound State in a Mixed-Valence State of SmS

et al. 2011

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“…The pressure dependence of the Sm valency was studied by Annese et al (2006) using 2p3d-RXES from 3 to 18 GPa at room temperature. The results (Fig.…”

Section: Connection To Metal-insulator Transition: Smsmentioning

confidence: 99%

Inelastic x-ray scattering by electronic excitations under high pressure

Rueff¹,

Shukla²

2010

Rev. Mod. Phys.

173

140

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Investigating electronic structure and excitations under extreme conditions gives access to a rich variety of phenomena. High pressure typically induces behavior such as magnetic collapse and the insulator-metal transition in 3d transition metals compounds, valence fluctuations or Kondo-like characteristics in f -electron systems, and coordination and bonding changes in molecular solids and glasses. This article reviews research concerning electronic excitations in materials under extreme conditions using inelastic x-ray scattering (IXS). IXS is a spectroscopic probe of choice for this study because of its chemical and orbital selectivity and the richness of information it provides. Being an all-photon technique, IXS has a penetration depth compatible with high pressure requirements. Electronic transitions under pressure in 3d transition metals compounds and f -electron systems, most of them strongly correlated, are reviewed. Implications for geophysics are mentioned. Since the incident X-ray energy can easily be tuned to absorption edges, resonant IXS, often employed, is discussed at length. Finally studies involving local structure changes and electronic transitions under pressure in materials containing light elements are briefly reviewed.

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“…The paradox is that despite the valence (v) is intermediate as estimated by high energy spectroscopy 61,62 or Raman measurements, 63 the development of the correlation on cooling will lead to renormalize the electronic and magnetic properties either to the divalent limit (insulator ground state with 2+ magnetic form factor) for v < 2.8 or to the trivalent limit for v > 2.8 (metallic ground state with 3+ magnetic form factor). 58 The same renormalization has been observed for TmSe.…”

Section: 60mentioning

confidence: 99%

Skutterudite Results Shed Light on Heavy Fermion Physics

et al. 2008

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Only few selected examples among the great diversity of anomalous rare earth skutterudite are reviewed. Focus is first given on PrFe4P12 in comparison with URu2Si2. For PrFe4P12, great progress has been made on determining the nature of the order parameter (OP). A non magnetic order parameter with a multipolar component emerges here while for URu2Si2 the nature of the so-called hidden order remains mysterious. The two systems have several similarities in their temperature-pressure (T , P ) and magnetic field-temperature (H, T ) phase diagrams, in their spin dynamics, in their nesting character and in their high sensitivity to impurities. Advances on one side must stimulate new views on the other. Besides general considerations on the choice of the OP, a simple basic problem is the treatment of the Kondo coupling in a system with low charge carrier number for the cases of uncompensated and compensated semi-metal. An interesting problem is also the possible decoupling between exciton modes and itinerant carriers. KEYWORDS:The new skutterudite compounds such as PrFe 4 P 12 , SmOs 4 Sb 12 , SmFe 4 P 12 , CeOs 4 Sb 12 and CeFe 4 P 12 give new insights on the interplay between valence driven metal-insulator transitions, Kondo effect and magnetic long range order. A fancy point is that these compounds often seem to have an intermediate valence behaviour even when their valences are close to 3. The occurrence of well defined multipoles is often revealed by crossing the phase transition in temperature. Magnetic field will lead to recover the duality between localized and intermediate valence characters. To illustrate this particularity, a comparison is made with electronic conduction and magnetism in the intermediate valence system SmB 6 and TmSe and also with the ferromagnetic superconductor URhGe.

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Divalent-to-trivalent transition of Sm inSmS: Implications for the high-pressure magnetically ordered state

Cited by 33 publications

References 22 publications

Discontinuous Transition from a Real Bound State to Virtual Bound State in a Mixed-Valence State of SmS

Discontinuous Transition from a Real Bound State to Virtual Bound State in a Mixed-Valence State of SmS

Inelastic x-ray scattering by electronic excitations under high pressure

Skutterudite Results Shed Light on Heavy Fermion Physics

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