Regulation of antiphase boundary density in Fe3O4 thin films and its effect on the electrical and magnetic properties

Antiphase boundaries (APBs) widely exist in Fe3O4 thin films and affect significantly their electrical and magnetic properties. Here, effects of APBs on the electrical and magnetic properties of Fe3O4 thin films have been quantitatively investigated by a combined study of pulsed laser deposition, transmission electron microscopy (TEM) and first-principles calculations. It was revealed that the substrates affected greatly the density of APBs in Fe3O4 thin films but did not change the atomic structures of APBs. The APB density in the Fe3O4 (111) thin film grown on the MgO (111) substrate was one order of magnitude larger than that on the Al2O3 (0001) substrate. Atomic-scale TEM characterizations revealed that the APBs in the Fe3O4 thin films on both substrates had three types of atomic structures. Due to the higher APB density in the Fe3O4/MgO thin film, the electrical resistivity at 300 K was two orders of magnitude larger than that of the Fe3O4/Al2O3 thin film. Meanwhile, the saturation magnetization and the coercivity of the Fe3O4/MgO thin film were reduced by 86 % and 35 %, respectively. First-principles calculations suggested that the antiferromagnetic coupling was easily formed at all the three types of APBs, which led to the decrease of spin polarization and the increase of electrical resistance of the Fe3O4 thin films.