Evolution of magnetic properties in the vicinity of the Verwey transition in Fe3O4 thin films

TL;DR

This study investigates how magnetic properties like coercivity and remanence in Fe3O4 thin films change near the Verwey transition, revealing effects of substrate-induced strain, domain size, and film thickness on magnetic behavior.

Contribution

It provides new insights into the influence of substrate type, strain, and film thickness on the magnetic properties of Fe3O4 thin films near the Verwey transition.

Findings

Magnetic properties change rapidly at the Verwey transition temperature.

Domain size influences coercivity, while strain affects demagnetization.

Remanence ratio reversal depends on film thickness, with a critical thickness around 80 nm.

Abstract

We have systematically studied the evolution of magnetic properties, especially the coercivity and the remanence ratio in the vicinity of the Verwey transition temperature (TV ), of high-quality epitaxial Fe3O4 thin films grown on MgO (001), MgAl2O4 (MAO) (001), and SrTiO3 (STO) (001) substrates. We observed rapid change of magnetization, coercivity, and remanence ratio at TV , which are consistent with the behaviors of resistivity versus temperature [\r{ho}(T )] curves for the different thin films. In particular, we found quite different magnetic behaviors for the thin films onMgOfrom those onMAOand STO, inwhich the domain size and the strain state play very important roles. The coercivity is mainly determined by the domain size but the demagnetization process is mainly dependent on the strain state. Furthermore, we observed a reversal of remanence ratio at TV with thickness for the thin films grown on MgO: from a rapid enhancement for 40-nm- to a sharp drop for 200-nm-thick film, and the critical thickness is about 80 nm. Finally, we found an obvious hysteretic loop of coercivity (or remanence ratio) with temperature around TV , corresponding to the hysteretic loop of the \r{ho}(T ) curve, in Fe3O4 thin film grown on MgO.