Abnormal Magnetic Behaviors in Unique Square alpha-MnO2 Nanotubes

Systematic magnetic measurements have been performed in unique$\alpha - MnO_2$ square nanotubes synthesized by a facile hydrothermal method with microwave-assisted procedures. Unusual magnetic phenomena (abnormal magnetization verse temperature (M - T) behaviour, large and abnormal magnetization hysteresis loop horizontal shift (HHS) verse cooling field (HFC) behaviours (HHS - HFC) has been observed in these square nanotubes. These suggest the observation of large unfrozen orbital moment which also is the micro -original of observed large and abnormal horizontal shift (HHS). The findings demonstrated that engineering layered structures in nanoscale would create many unique nanostructures and unusual physicochemical behaviours.