Structure and magnetic properties evolution of nickel–zinc ferrite with lanthanum substitution

• Ni0.5Zn0.5LaxFe2–xO4 was synthesized by solid-state reaction at low temperatures for the first time.
• Change of lattice constants for Ni0.5Zn0.5LaxFe2–xO4 was explained.
• The magnetic properties of Ni0.5Zn0.5LaxFe2–xO4 can be precisely tailored by controlling the composition as well as the calcination temperature.

La3+-doped Ni–Zn ferrites with a nominal composition of Ni0.5Zn0.5LaxFe2–xO4 (where x=0–0.3) are prepared by solid-state reaction at low temperatures. X-ray diffraction data shows that single phase Ni0.5Zn0.5Fe2O4 is obtained at 600 °C, but all samples consist of the main spinel phase in combination of a small amount of a foreign LaFeO3 phase after doping. When the precursor is calcined at 900 °C, the lattice constants of the ferrites initially increase after La3+ doping, but then become smaller with additional La3+ doping. The addition of La3+ results in a reduction of crystallite size. Magnetic measurement reveals that the specific saturation magnetization (Ms) of the as-prepared ferrites decreases with increasing La3+ substitution, while the coercivity (Hc) of Ni0.5Zn0.5LaxFe2–xO4 obtained above 800 °C increases with increasing La3+ substitution.

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