Magnetization processes in sputtered FeSiB thin films

Magnetic thin films have been obtained by rf sputtering on Si(3)N(4) substrates from a Fe(78)B(13)Si(9) target. The samples, with thickness t of 80 and 305 nm, are partially amorphous; crystalline fraction increases on increasing t. Magnetic force microscopy and magneto-optical images, performed at the remanence on both samples, indicate that for t=80 nm the average magnetization lies in the film plane, while for the largest thickness, it is oriented perpendicular to it. Static hysteresis loops have been measured at room temperature by means of a vectorial vibrating sample magnetometer with an auto-rotating head. In this way, two linearly independent components of the magnetization vector can be simultaneously acquired as a function of magnetic field either in the in-plane or out-of-plane configuration, at different angles with respect to a reference direction. In this work, the role of sample shape and magnetic anisotropy has been investigated by paying particular attention to the anhysteretic magnetization process and by considering the two-dimensional behavior of the magnetization vector. The negligible role of the in-plane shape anisotropy has been demonstrated in the specimen displaying out-of-plane anisotropy, whereas the effect of the local demagnetizing fields has been put in evidence in the sample with in-plane anisotropy.