Abstract
The pentachloride MoCl 5 adopts several molecular crystal structures, all comprising isolated Mo 2 Cl 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, ∈-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 2 Cl 10 molecules, indicating the potential for true molecular magnetism. Together, these results identify Mo 1-x W x Cl 5 as novel molecular crystals that combine spin 1/2 with strong magnetic anisotropy and exhibit surprisingly high Curie temperatures, considering their molecular nature.
Original language | English |
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Pages (from-to) | 2952-2959 |
Number of pages | 8 |
Journal | Chemistry of Materials |
Volume | 31 |
Issue number | 8 |
DOIs | |
State | Published - Apr 23 2019 |
Funding
This research was supported by the U.S. Department of Energy, Office of Science, Basic Energy Sciences, Materials Sciences and Engineering Division. This research used resources of the Compute and Data Environment for Science (CADES) at the Oak Ridge National Laboratory, which is supported by the Office of Science of the U.S. Department of Energy under contract no. DE-AC05-00OR22725.