Magnetic moment of MnO2
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Answer:
α-MnO2 nanotubes were fabricated using a hydrothermal technique. Li, Na and K ions were introduced into MnO2 nanotubes to tailor their magnetic properties. It was found that with a doping concentration lower than 12 at%, the nanotubes showed ferromagnetic-like ordering at low temperature (<50 K), while antiferromagnetic coupling dominated their physical behavior with doping concentrations beyond 12 at%. Such experimental phenomenon was in very good agreement with associated first principle calculations. The ferromagnetic-like ordering originates from the breaking of equivalence between two different Mn-O octahedrals in α-MnO2 due to the filling of alkaline ions in the tunnels. Both small charge transfer and lattice distortion play important roles in the ferromagnetic ordering.
Manganese dioxide, MnO2, has been widely used as catalysts, cathodes of lithium batteries and sieves in industry due to its unique physical and chemical properties, as well as its relative abundance in nature
Answer:
Manganese dioxide, MnO2, has been widely used as catalysts, cathodes of lithium batteries and sieves in industry due to its unique physical and chemical properties, as well as its relative abundance in nature1,2,3,4,5,6. As the precursor material for the lithium battery, an important feature of MnO2 is the presence of mesoporous channels formed by the stacking of MnO6 octahedrons, which can host K, Na, or Li ions. The framework of these mesopore channels, called octahedral molecular sieve structures, can form infinite alternating 1 × 1 and 2 × 2 tunnels. β-MnO2 has 1 × 1 tunnels, whilst α-MnO2 has 2 × 2 tunnels by sharing the edges and corners of the MnO6 octahedrons7,8. Detailed studies have shown that many elements can be doped into the structures due to the relatively large voids of these tunnels, such as cations of alkaline, alkaline earth elements, as well as heavy metals