Magnetoresistance and magnetization in submicron ferromagnetic gratings

Abstract

A technique for engineering micron and submicron scale structures from magnetic films of transition metals has been developed using a combination of electron- and ion-beam lithography enabling high-quality arrays of submicron magnetic Fe wires to be fabricated. This process can be used to fabricate novel devices from a variety of metal combinations which would not be possible by the usual liftoff metallization method. The structure and magnetic properties are reported of an epitaxial 25 nm Fe(001)/GaAs(001) film and the wire gratings which are fabricated from it. The width of the wires in the grating is 0.5 μm for all structures studied, but the separation of each wire is varied in the range 0.5 to 16 μm. An artificially induced shape anisotropy field of around 1 kG, consistent with a magnetostatic calculation, was observed for all separations studied. The field dependence of the magneto-optic Kerr effect and magnetoresistance (MR) data is consistent with a twisted magnetization configuration across the width of the sample beneath saturation for transverse applied fields. In this case, the detailed form of the field dependence of the MR is strikingly modified from that observed in the continuous film and is consistent with coherent rotation of the magnetization.

Strain and strain relief in Gd(0001) films on Mo(112)

“…In this scheme, magnetic domains can be created with the separation of misfit lines. This is similar to creating a "hard axis" as a consequence of shape along the applied field direction in our experiment, as is the case in a "magnetic grating" [19]. Such a model requires further data for confirmation, but is not unprecedented.…”

Exchange bias effects in ferromagnetic wires

“…Research on exchange biasing effect in ferromagnetic wires is therefore of interest because of its potential application in the information storage. Earlier works on magnetic wires were mostly concentrated on size dependence and orientation dependence on field [2,15,16]. Fraune et al [17] have investigated the size dependence of exchange bias in NiO/Ni nanostructures.…”

Coercive and anisotropy fields in patterned amorphous FeSi submicrometric structures

“…3, where it is compared with the loop of a reference unpatterned film of the same composition. Previous results in similar structures of pure transition metals or NiFe alloys show hysteresis loops with typical coercive and saturation fields above 100 Oe; for example, Shearwood et al 8 find H C Ϸ500 Oe in 1 m spaced lines made of epitaxial Fe͑001͒, and Adeyeye et al 9 obtain values of H C Ϸ200 Oe in 2 m separated policrystalline Ni 0.8 Fe 0.2 lines. In our case, the magnetic behavior in the array of Fe 0.7 Si 0.3 lines is also harder than in the unpatterned reference sample, with an increase of H C of almost one order of magnitude.…”

“…These structures have shown novel properties and are a new tool to test micromagnetic predictions; however, in general, a hardening of the magnetic material is observed as the lateral dimensions decrease below 1 m, so that the coercive and saturation fields of the structures increase by at least one order of magnitude respect to the unpatterned material, presenting typical values easily above a hundred Oersted. 8,9 This result could be an undesirable effect to fabricate certain devices for applications. The material crystalline microstructure with its particular defects is an important factor that could play a role in this behavior; for example, when the pattern dimensions are reduced to the 100 nm range, the grain size can become relevant influencing the magnetization reversal processes.…”