Heat accumulation and all-optical switching by domain wall motion in Co/Pd superlattices

Abstract

All-optical switching by domain wall motion has been obtained in Co/Pd superlattices with a TiS oscillator. Heat accumulation is part of the switching process for our experimental conditions. Numerical calculations point to a connection between domain wall motion and in-plane heat diffusion.

Heat diffusion in magnetic superlattices on glass substrates

“…The combination of large light absorption in the metallic film and small glass thermal conductivity can raise T acc above that of a thick metallic film. Heat accumulation and large temperature gradients in our samples explain the observed forces on magnetic domain walls during all-optical switching [26] and how a final demagnetized state can be obtained from both heat accumulation T acc and transient T tr ultrafast demagnetization [31].…”

Demagnetizing fields in all-optical switching

“…They confirm that demagnetized states are induced in Co/Pd. As in single-pulse AOS of GdFeCo [31] and cumulative AOS of Co/Pt superlattices [26], a demagnetized state is a precursor of cumulative AOS in Co/Pd [28]. The relation between demagnetization and AOS was examined in a model of demagnetizing fields and with micromagnetic simulations.…”

“…Ferromagnetic [Co/Pd] 4 superlattices were examined, in which cumulative AOS was observed with linearly-polarized light [28]. The samples were h = 4.1 nm thick with perpendicular magnetic anisotropy (PMA).…”

“…Right panel: sketch of magnetization time-dependence in GdFeCo with AOS domains starting after ∼ 10 ps at the center[31]. This takes a ms-range time interval in cumulative AOS of Co/Pd[28] and Co/Pt[26]. (b) Sketch of the experimental setup.…”

Ultrafast demagnetization at high temperatures

“…Ferromagnetic [Co/Pd] 4 superlattices were examined, in which cumulative all-optical switching (AOS) was observed with linearly-polarized light [19]. The samples were h = 4.1 nm thick with perpendicular magnetic anisotropy.…”