We have systematically studied the evolution of magnetic properties, especially the coercivity and the remanence ratio in the vicinity of the Verwey transition temperature $\left(T_V\right)$, of high-quality epitaxial ${\mathrm{Fe}}_3{\mathrm{O}}_4$ thin films grown on MgO (001), ${\mathrm{MgAl}}_2{\mathrm{O}}_4$ (MAO) (001), and ${\mathrm{SrTiO}}_3$ (STO) (001) substrates. We observed rapid change of magnetization, coercivity, and remanence ratio at $T_V$, which are consistent with the behaviors of resistivity versus temperature $\left[\rho \right(T\left)\right]$ curves for the different thin films. In particular, we found quite different magnetic behaviors for the thin films on MgO from those on MAO and STO, in which 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 $T_V$ 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 $T_V$, corresponding to the hysteretic loop of the $\rho \left(T\right)$ curve, in ${\mathrm{Fe}}_3{\mathrm{O}}_4$ thin film grown on MgO.

• Received 7 May 2017
• Revised 20 July 2017

DOI:https://doi.org/10.1103/PhysRevB.96.094405