Lateral Magnetically Modulated Multilayers by Combining Ion Implantation and Lithography

Abstract

The combination of lithography and ion implantation is demonstrated to be a suitable method to prepare lateral multilayers. A laterally, compositionally, and magnetically modulated microscale pattern consisting of alternating Co (1.6 µm wide) and Co-CoO (2.4 µm wide) lines has been obtained by oxygen ion implantation into a lithographically masked Au-sandwiched Co thin film. Magnetoresistance along the lines (i.e., current and applied magnetic field are parallel to the lines) reveals an effective positive giant magnetoresistance (GMR) behavior at room temperature. Conversely, anisotropic magnetoresistance and GMR contributions are distinguished at low temperature (i.e., 10 K) since the O-implanted areas become exchange coupled. This planar GMR is principally ascribed to the spatial modulation of coercivity in a spring-magnet-type configuration, which results in 180° Néel extrinsic domain walls at the Co/Co-CoO interfaces. The versatility, in terms of pattern size, morphology, and composition adjustment, of this method offers a unique route to fabricate planar systems for, among others, spintronic research and applications.

Research Update: Focused ion beam direct writing of magnetic patterns with controlled structural and magnetic properties

“…ion-induced alloying 5 or via a positive process by creating ferromagnetic elements by ion-induced change of chemical 6,7 or structural order 8 . Another possible approach is to use ion-induced chemical reactions to create magnetic patterns [9][10][11] .…”

Magnetization reversal in ferromagnetic wires patterned with antiferromagnetic gratings

“…26,27 For example, the magnetic properties of a continuous FM film partly covered with patterned AFM regions depend on the dimensions of the AFM and the strength of the exchange bias within the pinned regions, as shown in NiFe/FeMn 24 and NiFe/IrMn, 28 and Co films with O implantation showed local EB due to the formation of CoO in the implanted regions. 21 We showed earlier 29,30 that NiFe films patterned with IrMn stripes with a width of 100 to 500 nm and a period of 240 nm to 1 lm exhibited either single-step or two-step reversal depending on the IrMn dimensions. In this article, we extend this investigation to a structure consisting of an array of 200 nm wide NiFe stripes on which an orthogonal array of sub-500 nm wide IrMn stripes is patterned.…”

“…[11][12][13][14] In general, exchange bias and the blocking temperature decrease with decreasing dimensions, which has been attributed to formation of spin glass-like regions with weaker exchange bias at the edges of the patterned features. 17,18 Structures in which the FM and AFM layer are patterned into different dimensions [20][21][22][23][24] are much less well studied, even though FM layers with local regions of exchange bias may be useful in controlling domain walls in racetrack memory and logic devices 23 and in magnetic bit encoders 25 and mangnonic crystals. 26,27 For example, the magnetic properties of a continuous FM film partly covered with patterned AFM regions depend on the dimensions of the AFM and the strength of the exchange bias within the pinned regions, as shown in NiFe/FeMn 24 and NiFe/IrMn, 28 and Co films with O implantation showed local EB due to the formation of CoO in the implanted regions.…”

“…FM structures partly covered by an AFM layer can be made by depositing an FM/AFM bilayer and etching the AFM in selected areas, e.g., by ion beam etching, 31 but this can alter the magnetic properties of the FM layer. Ion bombardment through a mask can be used to locally modulate exchange bias, 21 but the spatial resolution of this process is limited. Alternatively, the FM and AFM layers may be patterned using two different lithography steps, but the processing compromises the quality of the FM/AFM interface which is critical for establishing exchange bias.…”

Voltage‐Induced ON Switching of Magnetism in Ordered Arrays of Non‐Ferrimagnetic Nanoporous Iron Oxide Microdisks

“…Only a few methods exist to tune the magnetic properties of materials after synthesis. Ion irradiation [ 12 ] and selective plastic deformation [ 13 ] have been used to induce structural disorder (atomic rearrangements) that cause irreversible changes in the magnetic behavior. The indirect coupling between spins and the electric or magnetic field components of light have been utilized to induce spin‐reorientation, demagnetization, modification of the magnetic structure, or even magnetization reversal without need of directly applying magnetic fields.…”