ZnZr doped barium ferrite single domain particles BaFe12-2xZnxZrxO19 with 0≤x≤0.8 were prepared by the chemical coprecipitation method. With increasing doping concentration x, the magnetocrystalline anisotropy and thus the coercivity was drastically decreased. This was mainly due to the substitution of Fe3+ ions in the magnetoplumbite structure and strongly affected by the selective occupation of nonmagnetic cations on sublattice sites. Compared with coercivity, the zero-field saturation magnetization decreased much slower. The particle size decreased with x, while both of the lattice parameters “a” and “c” increased. The high-field differential susceptibility showed an increase with increasing doping concentration x, revealing the breakdown of the magnetic collinear structure and subsequently increased fraction of surface canted spins. © 2000 American Institute of Physics.