A femtosecond twist to magnetism

Imagine being able to write magnetic information efficiently at THz data rates, creating such content using only the helicity of light. A consortium of researchers from institutes in San Diego, Nancy, Tsukuba and Kaiserslautern recently showed the feasibility of this process, using femtosecond laser pulses. In a recent issue of Science, Lambert et al.1 demonstrate all-optical helicity-dependent switching (AO-HDS) in ferromagnetic thin films with perpendicular magnetic anisotropy, [Co/Pt]n multilayers, as well as in granular recording media. Firing trains of femtosecond laser pulses while moving the laser spot across the specimen caused traces with up or down magnetization to be written when using left- or right-circularly polarized light, respectively, independently of the original magnetic state (see Figure 1).