Control of Magnetic Order in Spinel ZnFe$_2$O$_4$ Thin Films Through Intrinsic Defect Manipulation

TL;DR

This study investigates how intrinsic defect manipulation, specifically oxygen vacancies and cation redistribution, controls the magnetic properties of ZnFe₂O₄ thin films fabricated under different oxygen conditions.

Contribution

It demonstrates the ability to tune magnetic order in ZnFe₂O₄ thin films through controlled defect engineering and thermal treatments.

Findings

Magnetic response is enhanced by low-temperature annealing due to oxygen vacancies.

Higher annealing temperatures reduce magnetic response by cation redistribution.

Structural and electronic transitions correlate with magnetic property changes.

Abstract

We present a systematic study of the magnetic properties of semiconducting ZnFe$_2$O$_4$ thin films fabricated by pulsed laser deposition at low and high oxygen partial pressure and annealed in oxygen and argon atmosphere, respectively. The magnetic response is enhanced by annealing the films at 250$^{\circ}$C and diminished at annealing temperatures above 300$^{\circ}$C. The initial increase is attributed to the formation of oxygen vacancies after argon treatment, evident by the increase in the low energy absorption at $\sim$ 0.9 eV involving Fe$^{2+}$ cations. The weakened magnetic response is related to a decline in disorder with a cation redistribution toward a normal spinel configuration. The structural renormalization is consistent with the decrease and increase in oscillator strength of respective electronic transitions involving tetrahedrally (at $\sim$ 3.5 eV) and octahedrally (at $\sim$ 5.7 eV) coordinated Fe$^{3+}$ cations.