Identifying magnetic phases in chemically ordered and disordered FeAl thin films.

Direct magnetic writing of ferromagnetic nanoscale elements provides an alternative pathway for potential application in data storage or spintronic devices. Magnetic patterning due to local chemical disordering of FeAl thin films results in adjacent nanoscale regions that possess two different phases, a low-magnetization and high-coercive chemically ordered phase (non-irradiated ferromagnetic area, NIFM) and a high-magnetization and low-coercive chemically disordered phase (irradiated ferromagnetic area, IMF). Depending on the volume of NIFM and IFM phases, different interaction mechanisms were revealed.

Resonance behavior of embedded and freestanding microscale ferromagnets.

The ferromagnetic resonance of a disordered A2 FeAl ferromagnetic stripe, of dimensions 5 µm × 1 µm × 32 nm, has been observed in two vastly differing surroundings: in the first case, the ferromagnetic region was surrounded by ordered B2 FeAl, and in the second case it was free standing, adhering only to the oxide substrate. The embedded ferromagnet possesses a periodic magnetic domain structure, which transforms to a single domain structure in the freestanding case. The two cases differ in their dynamic response, for instance, the resonance field for the uniform (k = 0) mode at ~ 14 GHz excitation displays a shift from 209 to 194 mT, respectively for the embedded and freestanding cases, with the external magnetic field applied along the long axis.

Magnetic response of FeRh to static and dynamic disorder.

Atomic scale defects generated using focused ion as well as laser beams can activate ferromagnetism in initially non-ferromagnetic B2 ordered alloy thin film templates. Such defects can be induced locally, confining the ferromagnetic objects within well-defined nanoscale regions. The characterization of these atomic scale defects is challenging, and the mechanism for the emergence of ferromagnetism due to sensitive lattice disordering is unclear.

Strain Anisotropy and Magnetic Domains in Embedded Nanomagnets.

Nanoscale modifications of strain and magnetic anisotropy can open pathways to engineering magnetic domains for device applications. A periodic magnetic domain structure can be stabilized in sub-200 nm wide linear as well as curved magnets, embedded within a flat non-ferromagnetic thin film. The nanomagnets are produced within a non-ferromagnetic B2-ordered Fe Al thin film, where local irradiation by a focused ion beam causes the formation of disordered and strongly ferromagnetic regions of A2 Fe Al .

Ion induced ferromagnetism combined with self-assembly for large area magnetic modulation of thin films.

A highly versatile and scalable path to obtain buried magnetic nanostructures within alloy thin films, while maintaining a flat topography, is described. A magnetic pattern of nanoscale periodicity is generated over ∼cm2 areas by employing a B2 → A2 structural transition in the prototype Fe60Al40 thin alloy films. The phase transition was induced in the confined regions via ion-irradiation through self-assembled nanosphere masks.