Electron paramagnetic resonance in pyrolusite and cryptomelane manganese dioxides

Electron paramagnetic resonance spectroscopy has been applied to identify the singular structural features of pyrolusite (beta) and cryptomelane (alpha) manganese dioxides. At 77 K, the derivative linewidth of pyrolusite is reduced to that of cryptomelane and the M(S) = -3/2 spin states in cryptomelane are affected by the changes in crystal field. Isothermal heating of cryptomelane in air at 100 degrees C for two days affects the M(s) = -5/2 and M(s) = -3/2 levels. The results seem to confirm the partial collapse of the lattice due to release of molecular water on heating.