A First-Principles Study on the Structural, Electronic, Magnetic and Optical Properties of Lithium Zinc Ferrite Li_1-xZn_2xFe_5-xO₈

Zn-substituted lithium ferrites Li_1−xZn_2xFe_5−xO₈ (LZFO), in particular, have been widely used in microwave devices, since Zn-substitution could increase the saturation magnetization and lower the magneto-crystalline anisotropy, therefore reducing the coercive force and ferromagnetic resonance width.

In this work, we carried out first-principles study on the structural, electronic, magnetic and optical properties of Li–Zn ferrites Li_1−xZn_2xFe_5−xO₈ (LZFO, x=0, 0.25, 0.5, 0.75, and 1.0).

We applied the pseudopotential plane-wave method within the DFT framework to perform first-principles calculations, as implemented in VASP 5.4.4 and employed projector augmented wave (PAW) potentials.

In order to determine the lowest energy configuration for each composition, we performed structural optimizations for all possible configurations and determined their DFT total energies.

The figure shows the optimized structure with the lowest total energy for each composition.

By applying the DFT+U approach with U = 4 eV for the Fe 3d state, we found that the lattice constants satisfied Vegard's law, varying linearly with Zn content x.

And variation of total magnetization agreed well with experiment, and the band gaps both for spin up and down states changed along the quadratic functions.

Moreover, our calculations revealed that with the increase of Zn content, the static dielectric constant gradually decreased and the light absorption coefficient, reflective and refractive indices were reduced within the range of 0 to 8eV of photon energy, and the peak position of the electron energy loss were gradually lowered.

Our work provides atomistic insights into the structural, electronic, magnetic and optical properties of ferrite solid solutions by using first-principles calculations and thus contributes to the development of advanced electro-magnetic devices.

The research results were published in the "New Journal of Chemistry" under the title of "A first-principles study on the structural, electronic, magnetic and optical properties of lithium zinc ferrite Li_1-xZn_2xFe_5-xO₈"(https://doi.org/10.1039/d5nj04137f).