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Structure and magnetism of collapsed lanthanide elements

Research output: Contribution to journalArticle

Original languageEnglish
Article number024107
JournalPhysical Review B (Condensed Matter and Materials Physics)
Volume100
Issue number2
DOIs
Accepted/In press27 Jun 2019
Published22 Jul 2019

Documents

  • XC10340B

    XC10340B.pdf, 553 KB, application/pdf

    Uploaded date:27 Jun 2019

King's Authors

Abstract

Using synchrotron x-ray diffraction, we show that the long-accepted monoclinic structure of the "collapsed" high-pressure phases reported in seven lanthanide elements [Nd, Tb, Gd, Dy, Ho, Er, and (probably) Tm] is incorrect. In Tb, Gd, Dy, Ho, Er, and Tm we show that the collapsed phases have a 16-atom orthorhombic structure (oF16) not previously seen in the elements, whereas in Nd we show that it has an eight-atom orthorhombic structure (oF8) previously reported in several actinide elements. oF16 and oF8 are members of a new family of layered elemental structures, the discovery of which reveals that the high-pressure structural systematics of the lanthanides, actinides, and group-III elements (Sc and Y) are much more related than previously imagined. Electronic structure calculations of Tb, combined with quantum many-body corrections, confirm the experimental observation, and calculate that the collapsed orthorhombic phase is a ferromagnet, nearly degenerate with an antiferromagnetic state between 60 and 80 GPa. We find that the magnetic properties of Tb survive to the highest pressures obtained in our experiments (110 GPa). Further calculations of the collapsed phases of Gd and Dy, again using the correct crystal structure, show the former to be a type-A antiferromagnet, whereas the latter is ferromagnetic.

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