Fe3+ ions in amorphous solids: EPR on mechanically and chemically amorphized Al2O3

Stepwise amorphization of a low-level doped alpha-Al2O3 single crystal yiel ded powders without changes of the concentration and chemical nature of the dopants. Kind and degree of disturbances could be unambiguously monitored by the allowed and forbidden transitions of the Fe3+-cw-EPR in X-band using a Bruker bimodal cavity. Based on simulations diagonalizing the spin Hamil tonian for S = 5/2 it was possible to discriminate between regions as well as samples of structural order and disorder. The spectral pattern of the al lowed and forbidden transitions of Fe3+ ions together with the field-positi on-dependent saturation behaviour (4.2 K) allowed us to differentiate betwe en crystalline and amorphous components or regions of a sample.