Intermediate Yb valence in the Zintl phases Yb₁₄MSb₁₁(M=Zn,Mn,Mg): XANES, magnetism, and heat capacity

Journal Article · Wed Nov 11 00:00:00 EST 2020 · Physical Review Materials

DOI:https://doi.org/10.1103/physrevmaterials.4.114407· OSTI ID:1823402

He, Allan ^[1]; Wille, Elizabeth L. Kunz ^[1]; Moreau, Liane M. ^[2]; Thomas, Sean M. ^[3]; Lawrence, Jon M. ^[3]; Bauer, Eric D. ^[3]; Booth, Corwin H. ^[2]; Kauzlarich, Susan M. ^[1]

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1. Univ. of California, Davis, CA (United States)
2. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
3. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

${\mathrm{Yb}}_{14}\mathrm{Mn}{\mathrm{Sb}}_{11}$ is a magnetic Zintl compound as well as being one of the best high temperature $p$ -type thermoelectric materials. According to the Zintl formalism, which defines intermetallic phases where cations and anions are valence satisfied, this structure type is nominally made up of 14 ${\mathrm{Yb}}^{2+}$ , 1 ${\mathrm{MnSb}}_4^{9-}$ , 1 ${\mathrm{Sb}}_3^{7-}$ , and 4 ${\mathrm{Sb}}^{3-}$ atoms. When Mn is replaced by Mg or Zn, the Zintl defined motifs become 13 ${\mathrm{Yb}}^{2+}$ , 1 ${\mathrm{Yb}}^{3+}$ , 1 (Mg, Zn) ${\mathrm{Sb}}_4^{10-}$ , 1 ${\mathrm{Sb}}_3^{7-}$ , and 4 ${\mathrm{Sb}}^{3-}$ . The predicted existence of ${\mathrm{Yb}}^{3+}$ based on simple electron counting rules of the Zintl formalism calls the Yb valence of these compounds into question. X-ray absorption near-edge structure, magnetic susceptibility, and specific heat measurements on single crystals of the three analogs show signatures of intermediate valence Yb behavior and in particular, reveal the heavy fermion nature of ${\mathrm{Yb}}_{14}{\mathrm{MgSb}}_{11}$ . In these isostructural compounds, Yb can exhibit a variety of electronic configurations from intermediate ( $M=\mathrm{Zn}$ ), mostly 2+ ( $M=\mathrm{Mn}$ ), to 3+ ( $M=\mathrm{Mg}$ ). In all cases, there is a small amount of intermediate valency at the lowest temperatures. The amount of intermediate valency is constant for $M=\mathrm{Mn}$ , Mg and temperature dependent for $M=\mathrm{Zn}$ . The evolution of the Yb valence correlated to the transport properties of these phases is highlighted. The presence of Yb in this structure type allows for fine tuning of the carrier concentration and thereby the possibility of optimized thermoelectric properties along with unique magnetic phenomena.

• Research Organization: Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States)
• Sponsoring Organization: National Science Foundation (NSF); USDOE Office of Science (SC), Basic Energy Sciences (BES). Chemical Sciences, Geosciences & Biosciences Division
• Grant/Contract Number: AC02-05CH11231; AC02-76SF00515
• OSTI ID: 1823402
• Journal Information: Physical Review Materials, Journal Name: Physical Review Materials Journal Issue: 11 Vol. 4; ISSN 2475-9953
• Publisher: American Physical Society (APS)
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
chemical bonding
fermions
magnetism
specific heat
topological phases of matter