The site preference and magnetic properties of Zn-Zr substituted BaM ferrite ${\mathrm{BaFe}}_{12-x}{\mathrm{Zn}}_{x/2\mathrm{}}{\mathrm{Zr}}_{x/2\mathrm{}}{\mathrm{O}}_{19}$ nanoparticles with $x=0\mathrm{}–1.6$ have been studied using Mössbauer spectra and magnetic measurement. The results show that the magnetizations and magnetocrystalline anisotropies are closely related to the distributions of Zn-Zr ions on the five sites. The ${\mathrm{BaFe}}_{12-x}{\mathrm{Zn}}_{x/2\mathrm{}}{\mathrm{Zr}}_{x/2\mathrm{}}{\mathrm{O}}_{19}$ nanoparticles exhibit unusual saturation magnetization, which increase at low substitutions, reach a maximum and then decrease. Mössbauer spectra show that the Zn-Zr ions preferentially occupy the $2b$ and ${4f}_{\mathrm{VI}}$ sites. The preference for the ${4f}_{\mathrm{VI}}$ site is responsible for the anomalous increase in the magnetization at low Zn-Zr substitutions. At $x>~1.2$ the rapid decrease in the magnetizations is mainly attributed to a noncollinear magnetic structure. In addition, a monotonic decrease in the magnetocrystalline anisotropy with Zn-Zr substitutions has its origin in the preference of the Zn-Zr ions for the $2b$ and ${4f}_{\mathrm{VI}}$ sites.

• Received 3 April 2000

DOI:https://doi.org/10.1103/PhysRevB.62.6530