Application of Gas Field Ion Source to Patterning Nanoscale Magnetic Structures

Magnetic nanostructures are necessary components in a variety of sensors and devices, and in prototypes of spin-transport and spin-wave devices. In the past, broad beam ion-irradiation has been used to modify the magnetic properties via a variety of mechanisms, such as alloying, intermixing and structural disordering. In this contribution, we describe the application of the highly focused noble gas ion beam of a gas field ion source (GFIS), to the nanoscale modification of magnetic properties in alloy thin films. Materials in which the saturation magnetization (Ms) can be drastically enhanced via small changes to the atomic arrangement are ideal for the GFIS approach.
In B2 alloys such as Fe60Al40, Fe50Rh50 and Fe60V40, light noble gas ion-irradiation leads to the formation of anti-site defects, which increases the Fe – Fe nearest neighbor interactions and generates an associated increase of the Ms. The disorder induced by the GFIS beam is highly localized, with the extent of the magnetized region determined by lateral scattering of ions. These B2 alloys can be used as non-ferromagnetic templates, on to which the highly focused ion-beam acts as a magnetic writing stylus. Here we examine the conditions necessary and experimentally achievable limits for producing magnetic nanostructures using GFIS.