Site preference and magnetic properties for a perpendicular recording material: BaFe12-xZn,x/2Zrx/2O19 nanoparticles

The site preference and magnetic properties of Zn-Zr substituted BaM ferrit e BaFe12-xZnx/2Zrx/2O19 nanoparticles with x=0-1.6 have been studied using Mossbauer spectra and magnetic measurement. The results show that the magne tizations and magnetocrystalline anisotropies are closely related to the di stributions of Zn-Zr ions on the five sites. The BaFe12-xZnx/2Zrx/2O19 nano particles exhibit unusual saturation magnetization, which increase at low s ubstitutions, reach a maximum and then decrease. Massbauer spectra show tha t the Zn-Zr ions preferentially occupy the 2b and 4f(VI) sites. The prefere nce for the 4f(VI) site is responsible for the anomalous increase in the ma gnetization at low Zn-Zr substitutions. At x greater than or equal to 1.2 t he rapid decrease in the magnetizations is mainly attributed to a noncollin ear magnetic structure. In addition, a monotonic decrease in the magnetocry stalline anisotropy with Zn-Zr substitutions has its origin in the preferen ce of the Zn-Zr ions for the 2b and 4f(VI) sites.