Structural, optical, dielectric and magnetic properties of Mn1−xCoxO2 nanowires

• Relative permittivity of Co-doped MnO2 is 13 times higher than that of undoped MnO2.
• Large value of relative permittivity is due to presence of space charge polarization.
• Relative permittivity increases with temperature due to thermal motion of the molecules.
• Ferromagnetic behavior along with antiferromagnetic component was observed.
• Mixed valence state in MnO2 is responsible for the ferromagnetic behavior.

Undoped and Co-doped α-MnO2 nanowires were prepared by hydrothermal method at 140 °C. XRD revealed the tetragonal structure of α-MnO2 and Co doping did not affect the structure of α-MnO2. The morphology is found to be one dimensional nanowire, which is confirmed by SEM. The optical properties were studied by PL and FTIR. The PL emission spectra showed strong UV emission peak at 392 nm along with some weak emissions. The characteristic vibrational modes were analyzed by FTIR. The dielectric properties of undoped and doped samples were studied in the frequency range of 50 Hz to 1 MHz at different temperatures. Enhanced relative permittivity was observed for Co-doped MnO2 nanowire. The magnetic properties were analyzed by VSM, where ferromagnetic behavior along with antiferromagnetic component at room temperature was observed.