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Journal Article

Tuning the structural stability and spin-glass behavior in alpha-MnO2 nanotubes by Sn ion doping


Hu,  Zhiwei
Zhiwei Hu, Physics of Correlated Matter, Max Planck Institute for Chemical Physics of Solids, Max Planck Society;

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Liu, X., Xie, Y., Hu, Z., Lin, H.-J., Chen, C.-T., Dong, L., et al. (2022). Tuning the structural stability and spin-glass behavior in alpha-MnO2 nanotubes by Sn ion doping. Physical Chemistry Chemical Physics, 24, 12300-12310. doi:10.1039/d1cp05459g.

Cite as: https://hdl.handle.net/21.11116/0000-000A-93FD-3
A series of alpha-Mn1-xSnxO2 was synthesized by a simple hydrothermal method to shed light on the effect of substitution. Powder X-ray diffraction and scanning electron microscopy indicated that the particle size, crystal structure and morphology of the samples did not change with an increase of the Sn content. Sn, Mn, O and K elements were all uniformly distributed in the particles, which was observed using energy-dispersive X-ray spectroscopy. However, thermogravimetric analysis showed that the structural stability increased, and an increase of the Mn oxidation state from 3.8+ to nearly 4.0+ was observed by X-ray absorption spectroscopy. Besides, Sn-119 Mossbauer spectroscopy revealed that the Sn ions are all 4+ and incorporate into the lattice by replacing the Mn ions. The DC and AC magnetic susceptibility measurements down to 2 K exhibited a spin-glass phenomenon, and the freezing temperature, T-f, decreased from 44 K to 30.5 K with increasing Sn content. This indicates that increased disorder by nonmagnetic substitution results in the enhancement of the frustration in the lattice. Meanwhile, with doping of Sn4+ ions, the Curie-Weiss temperature increased, indicating enhanced antiferromagnetic interaction. Although the mixed valence of Mn3+ and Mn4+ almost disappeared, the reduction of charge disorder did not lead to the magnetic ordering in the sample. Since the Sn4+ ions are diamagnetic and have the same magnetic effect as cation vacancies in the lattice, so it is reasonable to believe that the spin-glass transition in alpha-MnO2 results from the cation vacancies rather than the mixture of Mn3+ and Mn4+.