High Pressure Phase Transformations in Heavy Rare Earth Metals and Connections to Actinide Crystal Structures

Vohra, Yogesh K.; Sangala, Bagvanth Reddy; Stemshorn, Andrew K.; Hope, Kevin M.

doi:10.1557/proc-1104-nn01-04

Cited by 12 publications

(11 citation statements)

References 10 publications

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“…This new phase can be indexed to the monoclinic C2/m phase with 4 atoms per unit cell and was previously reported in cerium under pressure [14]. This monoclinic phase is also similar to one reported in other heavy rare earth metals terbium [15], holmium [9], and thulium [11]. In a study on erbium [10], we have also examined orthorhombic Ibam proposed for praseodymium [16] but found the monoclinic C2/m to be the better fit for the low symmetry phase.…”

Section: Resultssupporting

confidence: 84%

Crystallographic phases in heavy rare earth metals under megabar pressures

Samudrala

Vohra

2012

J. Phys.: Conf. Ser.

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Section: Resultssupporting

confidence: 84%

Crystallographic phases in heavy rare earth metals under megabar pressures

Samudrala

Vohra

2012

J. Phys.: Conf. Ser.

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“…In analogy to actinides, the localized character of the lanthanide 4f level is expected to change under sufficient pressure. 7 In particular, a sudden pressure-induced drop in the molar volume, commonly termed "volume collapse", has been observed in Ce (16% volume collapse at 0.7 GPa), 8,9 Pr (9.1% at 21 GPa), 10 Eu (3% at 12 GPa), 11,12 Gd (5% at 59 GPa), 13,14 Tb (5% at 53 GPa), 15 Dy (6% at 73 GPa), 16 Ho (3% at 103 GPa), 17 Tm (1.5% at 120 GPa), 18 and Lu (5% at 90 GPa). 19 Such volume collapses are still the subject of debate, 3,5,6,[20][21][22][23][24][25] although widely thought to result from changes in the degree of 4f localization.…”

Section: Introductionmentioning

confidence: 99%

“…Eu (3% at 12 GPa), 11,12 Gd (5% at 59 GPa), 13,14 Tb (5% at 53 GPa), 15 Dy (6% at 73 GPa), 16 Ho (3% at 103 GPa), 17 Tm (1.5% at 120 GPa), 18 and Lu (5% at 90 GPa).…”

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confidence: 99%

Different routes to pressure-induced volume collapse transitions in gadolinium and terbium metals

et al. 2013

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The sudden decrease in molar volume exhibited by most lanthanides under high pressure is often attributed to changes in the degree of localization of their 4f -electrons. We give evidence, based on electrical resistivity measurements of dilute Y(Gd) and Y(Tb) alloys to 120 GPa, that the volume collapse transitions in Gd and Tb metals have different origins, despite their being neighbors in the periodic table. Remarkably, the change under pressure in the magnetic state of isolated Pr or Tb impurity ions in the nonmagnetic Y host appears to closely mirror corresponding changes in pure Pr or Tb metals. The collapse in Tb appears to be driven by an enhanced negative exchange interaction between 4f and conduction electrons under pressure (Kondo resonance) which, in the case of Y(Tb), dramatically alters the superconducting properties of the Y host, much like previously found for Y(Pr). In Gd our resistivity measurements suggest that a Kondo resonance is not the main driver for its volume collapse. X-ray absorption and emission spectroscopies clearly show that 4f local moments remain largely intact across both volume collapse transitions ruling out 4f band formation (delocalization) and valence transition models as possible drivers. The results highlight the richness of behavior behind the volume collapse transition in lanthanides and demonstrate the stability of the 4f level against band formation to extreme pressure.

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“…The same rare earth crystal structure sequence is also observed in individual members of the rare earth series under high pressure with the exception of divalent Eu and Yb and trivalent Sc. Structural transition studies on most rare earths have been carried out to megabar pressures (100-300 GPa) [1][2][3][4][5][6][7][8][9][10]. We present results from our work on the compression of yttrium to 177 GPa in this report.…”

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confidence: 99%

Structural phase transitions in yttrium under ultrahigh pressures

Samudrala¹,

Tsoi²,

Vohra³

2012

J. Phys.: Condens. Matter

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X-ray diffraction studies were carried out on the rare earth metal yttrium up to 177 GPa in a diamond anvil cell at room temperature. Yttrium was compressed to 37% of its initial volume at the highest pressure. The rare earth crystal structure sequence hcp → Sm type → dhcp → mixed(dhcp + fcc) → distorted fcc (dfcc) is observed in yttrium below 50 GPa. The dfcc (hR24) phase has been observed to persist in the pressure range of 50-95 GPa. A structural transition from dfcc to a low symmetry phase has been observed in yttrium at 99 ± 4 GPa with a volume change of - 2.6%. This low symmetry phase has been identified as a monoclinic C2/m phase, which has also been observed in other rare earth elements under high pressures. The appearance of this low symmetry monoclinic phase in yttrium shows that its electronic structure under extreme conditions resembles that of heavy rare earth metals, with a significant increase in d-band character of the valence electrons and possibly some f-electron states near the Fermi level.

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High Pressure Phase Transformations in Heavy Rare Earth Metals and Connections to Actinide Crystal Structures

Cited by 12 publications

References 10 publications

Crystallographic phases in heavy rare earth metals under megabar pressures

Crystallographic phases in heavy rare earth metals under megabar pressures

Different routes to pressure-induced volume collapse transitions in gadolinium and terbium metals

Structural phase transitions in yttrium under ultrahigh pressures

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