Evidence and role of excessive iron in the lattice of M-type barium hexaferrite synthesized by one-step spark plasma sintering method

M-type barium hexaferrite (BaM) compounds with excessive iron, BaFe12+xO19+1.5x (0 ⩽ x ⩽ 0.4), have been synthesized by spark plasma sintering method. The grains crystallized in plate-like form. The lattice parameters increased and the grain sizes decreased with increasing values of x. Specific saturation magnetization of 74.53–77.76 emu g−1 is greater than the theoretical value of BaM single crystal. Coercivity of 694.30–1146.58 Oe is far lower than that measured the BaM materials prepared by available methods.