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Title: Ferromagnetic Spin-1/2 Dimers with Strong Anisotropy in MoCl 5

Abstract

The pentachloride MoCl 5 adopts several molecular crystal structures, all comprising isolated Mo 2Cl 10 units with well-separated Mo–Mo magnetic dimers. Using magnetization measurements, single-crystal X-ray diffraction, and first-principles calculations, we confirm ferromagnetism with strong anisotropy below a Curie temperature of 22 K in α-MoCl 5, and report a fifth polymorph, ϵ-MoCl 5, that we find to be ferromagnetic below 14 K. Magnetization measurements indicate unquenched orbital moments antialigned with the spins. This is confirmed by first-principles calculations, which also predict an unusually strong magnetocrystalline anisotropy in α-MoCl 5 arising from spin–orbit coupling. An anisotropy field near 80 T is calculated, while a smaller but still substantial anisotropy field exceeding 12 T is realized experimentally. Further, increased anisotropy and Curie temperature are predicted when W is substituted for Mo. Similarly, strong magnetism and anisotropy are predicted for isolated Mo 2Cl 10 molecules, indicating the potential for true molecular magnetism. Altogether, these results identify Mo 1–xW xCl 5 as novel molecular crystals that combine spin 1/2 with strong magnetic anisotropy and exhibit surprisingly high Curie temperatures, considering their molecular nature.

Authors:
ORCiD logo [1]; ORCiD logo [1]; ORCiD logo [1]; ORCiD logo [1]
  1. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
OSTI Identifier:
1523742
Grant/Contract Number:  
[AC05-00OR22725]
Resource Type:
Accepted Manuscript
Journal Name:
Chemistry of Materials
Additional Journal Information:
[ Journal Volume: 31; Journal Issue: 8]; Journal ID: ISSN 0897-4756
Publisher:
American Chemical Society (ACS)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY

Citation Formats

McGuire, Michael A., Pandey, Tribhuwan, Mu, Sai, and Parker, David S. Ferromagnetic Spin-1/2 Dimers with Strong Anisotropy in MoCl5. United States: N. p., 2019. Web. doi:10.1021/acs.chemmater.9b00416.
McGuire, Michael A., Pandey, Tribhuwan, Mu, Sai, & Parker, David S. Ferromagnetic Spin-1/2 Dimers with Strong Anisotropy in MoCl5. United States. doi:10.1021/acs.chemmater.9b00416.
McGuire, Michael A., Pandey, Tribhuwan, Mu, Sai, and Parker, David S. Mon . "Ferromagnetic Spin-1/2 Dimers with Strong Anisotropy in MoCl5". United States. doi:10.1021/acs.chemmater.9b00416. https://www.osti.gov/servlets/purl/1523742.
@article{osti_1523742,
title = {Ferromagnetic Spin-1/2 Dimers with Strong Anisotropy in MoCl5},
author = {McGuire, Michael A. and Pandey, Tribhuwan and Mu, Sai and Parker, David S.},
abstractNote = {The pentachloride MoCl5 adopts several molecular crystal structures, all comprising isolated Mo2Cl10 units with well-separated Mo–Mo magnetic dimers. Using magnetization measurements, single-crystal X-ray diffraction, and first-principles calculations, we confirm ferromagnetism with strong anisotropy below a Curie temperature of 22 K in α-MoCl5, and report a fifth polymorph, ϵ-MoCl5, that we find to be ferromagnetic below 14 K. Magnetization measurements indicate unquenched orbital moments antialigned with the spins. This is confirmed by first-principles calculations, which also predict an unusually strong magnetocrystalline anisotropy in α-MoCl5 arising from spin–orbit coupling. An anisotropy field near 80 T is calculated, while a smaller but still substantial anisotropy field exceeding 12 T is realized experimentally. Further, increased anisotropy and Curie temperature are predicted when W is substituted for Mo. Similarly, strong magnetism and anisotropy are predicted for isolated Mo2Cl10 molecules, indicating the potential for true molecular magnetism. Altogether, these results identify Mo1–xWxCl5 as novel molecular crystals that combine spin 1/2 with strong magnetic anisotropy and exhibit surprisingly high Curie temperatures, considering their molecular nature.},
doi = {10.1021/acs.chemmater.9b00416},
journal = {Chemistry of Materials},
number = [8],
volume = [31],
place = {United States},
year = {2019},
month = {3}
}

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