Engineering spin textures for magnetoelectronics

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Sub-micron structuring of silicon using femtosecond laser interferometry

Publication . Oliveira, Vitor; Vilar, R.; Serra, R.; Oliveira, J.C.; Polushkin, N.I.; Conde, O.

We report the fabrication of planar sub-micron gratings in silicon with a period of 720 nm using a modified Michelson interferometer and femtosecond laser radiation. The gratings consist of alternated stripes of laser ablated and unmodified material. Ablated stripes are bordered by parallel ridges which protrude above the unmodified material. In the regions where ridges are formed, the laser radiation intensity is not sufficient to cause ablation. Nevertheless, melting and a significant temperature increase are expected, and ridges may be formed due to expansion of silicon during resolidification or silicon oxidation. These conclusions are consistent with the evolution of the stripes morphology as a function of the distance from the center of the grating.

2013-12Journal article

Open access

Phase-change magnetic memory: Rewritable ferromagnetism by laser quenching of chemical disorder in Fe60Al40 alloy

Publication . Polushkin, Nikolay I.; Oliveira, Vitor; Vilar, R.; He, M.; Shugaev, Maxim; Zhigilei, Leonid

High-intensity laser irradiation can effectively couple to practically all kinds of materials, causing modification of their physical properties due to laser-induced phase transformations. This gives rise to a broad field of laser micro- and nanofabrication with its various technological applications. We demonstrate that, in a 40-nm-thick film of Fe60Al40 alloy, a short laser pulse is capable of (re)writing the ferromagnetism observed at room temperature (RT). The energy of the pulse generating a ferromagnetic region has to be sufficiently high to induce melting of the Fe60Al40 layer, while the ferromagnetic state can be erased by various kinds of lower-intensity thermal treatment. This cycling of RT ferromagnetism can be explained in terms of the chemical order (B2)-disorder (A2) phase transition in the Fe60Al40 crystal lattice, which is affected by laser-induced melting and rapid resolidification. Our finding has implications for the development of a magnetic memory technology that would use the reversibility of the modulus of the magnetization vector instead of its direction. This promises to circumvent the problem of the superparamagnetic limit for magnetic data storage density.

2018-08-17Journal article

Restricted access