Tailoring structure and magnetic characteristics of strontium hexaferrite via Al doping engineering

Emerging structure and magnetic properties of Al3+-modified SrFe12O19 M-type hexaferrite system (SrAlxFe12−xO19) had been studied in detail via doping engineering. With Al3+ ion nominal content ranging from 0 to 4 (0≤x≤4), the lattice parameters decrease due to the substitution of Fe3+ ions by smaller Al3+ ions, and the magnetization shows a continuous reduction with the increasing of Al content. For the coercivity, its value initially increases, reaching a maximum value of 16,876.9 Oe at x=3, and then reduces with the Al content further increase. When all the Fe3+ ions (x=4) are replaced by Al3+ ions, the net magnetic moment will be closed to zero, that will weaken the exchange interaction between Fe3+ ions, resulting in decrease of coercivity sharply and transformation ferrimagnetism into antiferromagnetism. The mechanism of the improvement of the magnetic properties induced by Al doping is discussed in the present work.