Hydrothermal Synthesis and Magnetic Properties of Hexagonal Sr 3 Co 2 Fe 24 O 41 Particles

Hexagonal Sr 3 Co 2 Fe 24 O 41 (SrZ) ferrites were synthesized by a hydrothermal method. The effects of atomic ratio of Fe/Sr ( $R_{\mathrm {Sr/Fe}}=x /8$ ), hydrothermal reaction temperature ( $T_{H}$ ) and reaction time ( $t_{H}$ ), and the sintering temperature ( $T_{s}$ ) on the phase composition, microstructures, and magnetic properties of SrZ particles were investigated. In order to obtain a single Z-phase, $x$ value in the initiative materials must be equal to 1.25. When $x$ value is less than 1.25, $\alpha $ -Fe 2 O 3 , Sr 3 Fe 2 (OH) 12 , and unknown phase appear in the precursor powders, ultimately leading to impurity phases in the sintered specimens. When $x$ value is $>1.5$ , synthesis of Z-phase is difficult, since superfluous $\alpha $ -Fe 2 O 3 phase exists with M-phase and spinel phase in the precursor powders. Hexagonal SrZ sheets of $\sim 2~\mu \text{m}$ wide and dozens of nanometers thick were obtained under optimized conditions. The magnetic measurements reveal that the easy magnetization axis of hexagonal Z-phase sheets at room temperature lies in the $c$ plane.