Edge-modulated perpendicular magnetic anisotropy in [Co/Pd]n and L10- FePt thin film wires

Thickness modulation at the edges of nanostructured magnetic thin films is shown to have important effects on their perpendicular magnetic anisotropy. Thin film wires with tapered edges were made from [Co/Pd]20 multilayers or L10-FePt films using liftoff with a double-layer resist. The effect of edge taper on the reversal process was studied using magnetic force microscopy (MFM) and micromagnetic modeling. In [Co/Pd]20 the anisotropy was lower in the tapered edge regions which switched at a lower reverse field compared to the center of the wire. The L10-FePt wires showed opposite behavior with the tapered regions exhibiting higher anisotropy. Thin film materials with strong perpendicular magnetic anisotropy (PMA) such as [Co/Pd]n multilayers and L10-FePt are useful for a variety of magnetic recording and logic devices because their high anisotropy promotes thermal stability at low dimensions [15]. The PMA in [Co/Pd]n multilayers originates from interfacial anisotropy which is induced by lattice mismatch strain [6-8]. A greater PMA is achieved by increasing the number of interfaces or optimizing the interfacial structure in [Co/Pd]n multilayers [1, 9]. In contrast, the high PMA in a (001)-oriented L10-FePt film, which can be described as