Processing and cation redistribution of MnZn ferrites via high-energy ballmilling

We have produced MnZn ferrites via high-energy ball milling (HEBM) of eleme ntal oxides MnO, ZnO, and Fe2O3. X-ray diffraction (XRD) indicates a pure p hase spinel forms after 21 h of HEBM. Extended x-ray absorption fine struct ure (EXAFS) analysis shows a nonequilibrium cation distribution, with an un usually high population of Zn cations on the octahedral sublattice. We then used EXAFS modeling to study cation site occupancy in an equilibrium MnZn- ferrite standard subjected to HEBM. We found that HEBM produces an increase d preference for octahedral-site occupation among all cations for milling d urations up to 300 min. After an initial improvement in magnetic properties , the magnetization diminishes steadily throughout this interval. With furt her increases in milling duration these structural and magnetic trends reve rse, possibly due to annealing effects evidenced by XRD. (C) 1998 American Institute of Physics. [S0021-8979(98)42311-9].