Eu5Al3Sb6: Al4Tetrahedra Embedded in a Rock-Salt-Like Structure

Allan He, Zihao Shen, Haozhe Wang, Weiwei Xie, Zhen Wang, Luis Garay, James C. Fettinger, Raphaël P. Hermann, Yimei Zhu, Valentin Taufour, Susan M. Kauzlarich

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Abstract

The new Eu5Al3Sb6 phase has been successfully synthesized as a pure phase through Sn flux methods yielding large, high-quality crystals. This structure type features disordered Al clusters that appear in the form of dual tetrahedra. It crystallizes in the monoclinic C2/m space group exhibiting a rock-salt-like Eu-Sb framework with [Al4] tetrahedra replacing some of the cationic Eu atoms (space group: C2/m, a = 8.151(1) Å, b = 14.181(2) Å, c = 8.145(1) Å, β = 109.577(2)°). The structure models the [Al4] as dual tetrahedra with the Al atom sites 37.5% occupied along with Eu present on the central site at 8% occupancy and the remainder of the site being vacant. The presence of the [Al4] cluster is further supported by HRTEM. Electronic structure calculations show that this material is a semimetal with observed band crossings close to the Fermi level. Strong Al-Sb antibonding interactions were found from COHP calculations close to the Fermi level and provide the rationale for the deficiency of the Al cluster. Mössbauer spectroscopy on Eu-151 and Sb-121 provides oxidation states of 2+ and 3- along with the local environment. Magnetic susceptibility measurements can be described well with a Curie-Weiss law where an effective moment of 7.80 μB/mol Eu is obtained, consistent with Eu2+, and show canted antiferromagnetic behavior below 10 K. Temperature dependent resistivity shows a Kondo-like low-temperature upturn caused by enhanced scattering of the itinerant electrons with the 4f orbitals of Eu.

Original languageEnglish
Pages (from-to)5009-5019
Number of pages11
JournalChemistry of Materials
Volume34
Issue number11
DOIs
StatePublished - Jun 14 2022

Funding

This work was supported by NSF DMR-2001156. Z.S. and V.T. acknowledge support from the UC Laboratory Fees Research Program (LFR-20-653926) and the Physics Liquid Helium Laboratory Fund. W.X. and H.Z.W. at Rutgers were supported by NSF- DMR-2053287. The electron microscopy work at BNL was supported by U.S. DOE-BES, Materials Sciences and Engineering Division, under Contract No. DESC0012704. Mössbauer spectral work by R.P.H. was supported by the U.S. Department of Energy (DOE), Office of Science, Office of Basic Energy Sciences (BES), Materials Sciences and Engineering Division. We thank P. Klavins (UCD Physics) for useful discussions.

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