Possible magnetic significance of faults and polytypes in R 2 Co 17 compounds

A description of the structures of R 2 Co 17 as layer structures is presented and possible stacking faults and dislocations involving the layer planes are described. The significance of the planar defects observed in R 2 Co 17 and structurally similar compounds and the effects of the various rare earth ion symmetries for the 2H, 1R, 4H, 5H and 6H(1) and 6H(2) possible modifications for R 2 Co 17 compounds on magnetic anisotropy and magnetostriction are discussed. Finally the possible influence of stacking faults on these properties is considered.