Enhancement of ferromagnetic properties in BiFeO3 polycrystalline ceramic by La doping

The authors present the structure transformation and magnetic properties of ${\mathrm{Bi}}_{1-x}{\mathrm{La}}_x\mathrm{Fe}{\mathrm{O}}_3$ $(x=0.0–0.15)$ ceramics prepared by a conventional solid-state reaction processing. Magnetic measurements reveal that remnant magnetization of 15% La-doped $\mathrm{Bi}\mathrm{Fe}{\mathrm{O}}_3$ has enhanced about 20 times as compared to pure $\mathrm{Bi}\mathrm{Fe}{\mathrm{O}}_3$ . It is the structural phase transition $(R3c–C222)$ near $x=0.15$ that destructs the spin cycloid, and thus enhances the ferromagnetic properties significantly. In these ${\mathrm{Bi}}_{1-x}{\mathrm{La}}_x\mathrm{Fe}{\mathrm{O}}_3$ ceramic samples, besides the known antiferromagnetic Néel temperature $T_{N1}\sim 615\mathrm{K}$ , another Néel temperature $T_{N2}\sim 260\mathrm{K}$ can be observed due to the trace impurity phase of ${\mathrm{Bi}}_2{\mathrm{Fe}}_4{\mathrm{O}}_9$ in these ceramic samples.