Synthesis, crystal structure, and magnetism of A{sub 2}Co{sub 12}As{sub 7} (A=Ca, Y, Ce–Yb)

Journal Article · Fri Apr 15 04:00:00 EDT 2016 · Journal of Solid State Chemistry

DOI:https://doi.org/10.1016/J.JSSC.2015.08.038· OSTI ID:22584036

Tan, Xiaoyan ^[1]; Ovidiu Garlea, V. ^[2]; Chai, Ping ^[1]; Geondzhian, Andrey Y. ^[3]; Yaroslavtsev, Alexander A. ^[3]; European XFEL GmbH, 22761 Hamburg ^[4]; Xin, Yan ^[5]; Menushenkov, Alexey P. ^[3]; Chernikov, Roman V. ^[6]; Shatruk, Michael ^[1]

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1. Department of Chemistry and Biochemistry, Florida State University, Tallahassee, FL 32306 (United States)
2. Quantum Condensed Matter Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831 (United States)
3. National Research Nuclear University “Moscow Engineering Physics Institute”, 115409 Moscow (Russian Federation)
4. Germany
5. National High Magnetic Field Laboratory, Tallahassee, FL 32310 (United States)
6. DESY Photon Science, 22603 Hamburg (Germany)

Ternary intermetallics, A{sub 2}Co{sub 12}As{sub 7} (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 P6{sub 3}/m variant of the Zr{sub 2}Fe{sub 12}P{sub 7} 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 A{sub 2}Co{sub 12}As{sub 7} 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 Ce{sub 2}Co{sub 12}As{sub 7} and Nd{sub 2}Co{sub 12}As{sub 7}, respectively. - Graphical abstract: Title arsenides were synthesized by Bi‐flux method. They exhibit mixed valence for A = Ce, Eu, Yb, ferrimagnetism for A = Ca, Y, Pr–Sm, and ferromagnetism for A = Eu–Tm. - Highlights: • A2Co12As7 (A=Ca, Y, Ce–Yb) were synthesized in Bi flux. • Ce, Eu, Yb exhibit mixed valence in the corresponding structures. • The character of 3d‐4f magnetic coupling changes at the half‐filled f shell. • Materials behave as ferrimagnets for A=Ca, Y, Pr–Sm and as ferromagnets for A=Eu–Yb.

• OSTI ID: 22584036
• Journal Information: Journal of Solid State Chemistry, Journal Name: Journal of Solid State Chemistry Vol. 236; ISSN 0022-4596; ISSN JSSCBI
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
ABSORPTION
ABSORPTION SPECTROSCOPY
ANNEALING
ANTIFERROMAGNETISM
ARSENIDES
CRYSTAL GROWTH
CRYSTALS
FERRIMAGNETISM
FERROMAGNETISM
FLUX SYNTHESIS
GROUND STATES
HEXAGONAL LATTICES
INTERMETALLIC COMPOUNDS
NEUTRON DIFFRACTION
NEUTRONS
OXIDATION
RARE EARTHS
SYNTHESIS
X RADIATION
X-RAY SPECTROSCOPY