Self-Demagnetizing Effects in Thin Films with Finite Lateral Dimensions

To analyze the shape effects on magnetic properties in films, it is common to assume some direction as very large in relation to another if the aspect ratio reaches 20 times. Thus, models based on oblate ellipsoids are assumed to estimate the format factor of the given geometry. In the present work, an experimental analysis complemented by simulations was carried out in 50 nm Permalloy (Py) thin films with 2000 nm circular-shaped area. Another geometry contemplates 50 nm Py films covering an ellipse-like format area, with 1000 nm of minor axes and 4000 nm of major axis. Magnetization curves, with the external magnetic field at different orientations, show differences in results if compared the two geometries. Experimental results and numerical simulations show that, even being large areas, the films format is relevant for aspect ratio (thickness to lateral dimensions) of 40 times.