Synthesis, crystal structure, and magnetism of A2Co12As7 (A=Ca, Y, Ce-Yb)

Xiaoyan Tan; V. Ovidiu Garlea; Ping Chai; Andrey Y. Geondzhian; Alexander A. Yaroslavtsev; Yan Xin; Alexey P. Menushenkov; Roman V. Chernikov; Michael Shatruk

doi:10.1016/j.jssc.2015.08.038

Synthesis, crystal structure, and magnetism of A₂Co₁₂As₇ (A=Ca, Y, Ce-Yb)

Xiaoyan Tan, V. Ovidiu Garlea, Ping Chai, Andrey Y. Geondzhian, Alexander A. Yaroslavtsev, Yan Xin, Alexey P. Menushenkov, Roman V. Chernikov, Michael Shatruk

Direct Geometry

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Abstract

Ternary intermetallics, A₂Co₁₂As₇ (A=Ca, Y, Ce-Yb), have been synthesized by annealing mixtures of elements in molten Bi at 1223 K. The materials obtained crystallize in the P6₃/m variant of the Zr₂Fe₁₂P₇ structure type. The unit cell volume shows a monotonic decrease with the increasing atomic number of the rare-earth metal, with the exception of Ce-, Eu-, and Yb-containing compounds. An examination of these outliers with X-ray absorption near edge structures (XANES) spectroscopy revealed mixed valence of Ce, Eu, and Yb, with the average oxidation states of +3.20(1), +2.47(5), and +2.91(1), respectively, at room temperature. Magnetic behavior of A₂Co₁₂As₇ is generally characterized by ferromagnetic ordering of Co 3d moments at 100-140 K, followed by low-temperature ordering of rare-earth 4f moments. The 3d-4f magnetic coupling changes from antiferromagnetic for A=Pr-Sm to ferromagnetic for A=Ce and Eu-Yb. Polarized neutron scattering experiments were performed to support the postulated ferro- and ferrimagnetic ground states for Ce₂Co₁₂As₇ and Nd₂Co₁₂As₇, respectively.

Original language	English
Pages (from-to)	147-158
Number of pages	12
Journal	Journal of Solid State Chemistry
Volume	236
DOIs	https://doi.org/10.1016/j.jssc.2015.08.038
State	Published - Apr 1 2016

Funding

This work was supported by the National Science Foundation award DMR-1507233 to M.S. The work at the Oak Ridge National Laboratory was sponsored by the Scientific User Facilities Division, Office of Basic Energy Sciences, U.S. Department of Energy (DOE) . V.O.G. thanks the help provided by the HYSPEC instrument team, B. Winn and M. Graves-Brook, during the polarized neutron scattering study. The TEM work was carried out at the electron microscopy facility at FSU which is funded and supported by the FSU Research Foundation, National High Magnetic Field Laboratory ( NSF - DMR-0654118 ), and the State of Florida . The authors acknowledge Helmholtz-Zentrum Berlin and MAX IV Laboratory for providing the time at mySpot and I811 beamlines and Dr. Ivo Zizak (HZB), Dr. S. Carlson and Dr. K. Sigfridsson (MAX IV) for support during the experiment. A.P.M. and A.A.Y. thank the Russian Science Foundation (Project 14-22-00098 ) for support.

Keywords

Arsenides
Crystal growth
Flux synthesis
Itinerant magnetism
Mixed valence

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10.1016/j.jssc.2015.08.038

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@article{5aa3cf899d554f5ebb6dcafbec90f48c,

title = "Synthesis, crystal structure, and magnetism of A2Co12As7 (A=Ca, Y, Ce-Yb)",

abstract = "Ternary intermetallics, A2Co12As7 (A=Ca, Y, Ce-Yb), have been synthesized by annealing mixtures of elements in molten Bi at 1223 K. The materials obtained crystallize in the P63/m variant of the Zr2Fe12P7 structure type. The unit cell volume shows a monotonic decrease with the increasing atomic number of the rare-earth metal, with the exception of Ce-, Eu-, and Yb-containing compounds. An examination of these outliers with X-ray absorption near edge structures (XANES) spectroscopy revealed mixed valence of Ce, Eu, and Yb, with the average oxidation states of +3.20(1), +2.47(5), and +2.91(1), respectively, at room temperature. Magnetic behavior of A2Co12As7 is generally characterized by ferromagnetic ordering of Co 3d moments at 100-140 K, followed by low-temperature ordering of rare-earth 4f moments. The 3d-4f magnetic coupling changes from antiferromagnetic for A=Pr-Sm to ferromagnetic for A=Ce and Eu-Yb. Polarized neutron scattering experiments were performed to support the postulated ferro- and ferrimagnetic ground states for Ce2Co12As7 and Nd2Co12As7, respectively.",

keywords = "Arsenides, Crystal growth, Flux synthesis, Itinerant magnetism, Mixed valence",

author = "Xiaoyan Tan and {Ovidiu Garlea}, V. and Ping Chai and Geondzhian, {Andrey Y.} and Yaroslavtsev, {Alexander A.} and Yan Xin and Menushenkov, {Alexey P.} and Chernikov, {Roman V.} and Michael Shatruk",

year = "2016",

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doi = "10.1016/j.jssc.2015.08.038",

language = "English",

volume = "236",

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journal = "Journal of Solid State Chemistry",

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TY - JOUR

T1 - Synthesis, crystal structure, and magnetism of A2Co12As7 (A=Ca, Y, Ce-Yb)

AU - Tan, Xiaoyan

AU - Ovidiu Garlea, V.

AU - Chai, Ping

AU - Geondzhian, Andrey Y.

AU - Yaroslavtsev, Alexander A.

AU - Xin, Yan

AU - Menushenkov, Alexey P.

AU - Chernikov, Roman V.

AU - Shatruk, Michael

PY - 2016/4/1

Y1 - 2016/4/1

N2 - Ternary intermetallics, A2Co12As7 (A=Ca, Y, Ce-Yb), have been synthesized by annealing mixtures of elements in molten Bi at 1223 K. The materials obtained crystallize in the P63/m variant of the Zr2Fe12P7 structure type. The unit cell volume shows a monotonic decrease with the increasing atomic number of the rare-earth metal, with the exception of Ce-, Eu-, and Yb-containing compounds. An examination of these outliers with X-ray absorption near edge structures (XANES) spectroscopy revealed mixed valence of Ce, Eu, and Yb, with the average oxidation states of +3.20(1), +2.47(5), and +2.91(1), respectively, at room temperature. Magnetic behavior of A2Co12As7 is generally characterized by ferromagnetic ordering of Co 3d moments at 100-140 K, followed by low-temperature ordering of rare-earth 4f moments. The 3d-4f magnetic coupling changes from antiferromagnetic for A=Pr-Sm to ferromagnetic for A=Ce and Eu-Yb. Polarized neutron scattering experiments were performed to support the postulated ferro- and ferrimagnetic ground states for Ce2Co12As7 and Nd2Co12As7, respectively.

AB - Ternary intermetallics, A2Co12As7 (A=Ca, Y, Ce-Yb), have been synthesized by annealing mixtures of elements in molten Bi at 1223 K. The materials obtained crystallize in the P63/m variant of the Zr2Fe12P7 structure type. The unit cell volume shows a monotonic decrease with the increasing atomic number of the rare-earth metal, with the exception of Ce-, Eu-, and Yb-containing compounds. An examination of these outliers with X-ray absorption near edge structures (XANES) spectroscopy revealed mixed valence of Ce, Eu, and Yb, with the average oxidation states of +3.20(1), +2.47(5), and +2.91(1), respectively, at room temperature. Magnetic behavior of A2Co12As7 is generally characterized by ferromagnetic ordering of Co 3d moments at 100-140 K, followed by low-temperature ordering of rare-earth 4f moments. The 3d-4f magnetic coupling changes from antiferromagnetic for A=Pr-Sm to ferromagnetic for A=Ce and Eu-Yb. Polarized neutron scattering experiments were performed to support the postulated ferro- and ferrimagnetic ground states for Ce2Co12As7 and Nd2Co12As7, respectively.

KW - Arsenides

KW - Crystal growth

KW - Flux synthesis

KW - Itinerant magnetism

KW - Mixed valence

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