Modulation on the magnetic and electrical properties of Fe3O4 thin films through strain relaxation

A series of Fe3O4 thin films with growth temperature ranging from 400 to 600 degrees C are prepared by magnetron sputtering on alpha -Al2O3 (0001). XRD and XPS measurements indicate that all the samples are pure Fe3O4 (111) epitaxial thin films. Microscopic strain is highly sensitive to the growth temperature. As a result, the magnetic and electrical measurements show some interesting phenomena related to the strain relaxation. The saturation magnetization demonstrates a monotonous increase in relative change as large as 85.9% originating from the strain relaxation effect. The improvement of magnetic anisotropy in Fe3O4 thin films is attributed to the reduction of strain-induced anisotropy. However, the resistivity changes suddenly at the growth temperature of 450 degrees C, which is dominated by mesoscopic grain size rather than microscopic strain.