Novel micromagnetics for high-temperature applications and modeling of ultra-fast laser-induced magnetization dynamics

Several recently appeared applications such as spin-caloritronics, heat-assisted magnetic recording or ultra-fast laser induced magnetization dynamics involve high temperatures. The standard micro-magnetic approach is known to fail there due to the conservation of the magnetization length. Recently proposed micromagnetics based on the Landau-Lifshitz-Bloch (LLB) equation overcomes this limitation and extends the micromagnetic modeling up to and above the Curie temperature. The LLB micromagnetics is naturally based on the multi-scale approach via the incorporation of the ab-initio and atomistic information. While the classical LLB equation is based on the atomistic spin dynamics, its quantum version incorporates the scattering mechanisms. The two-sublattie LLB equation is useful to describe distinct dynamics of the components of an alloy. The most successful example of the novel micromagnetics is the modeling of the ultra-fast magnetization dynamics. The FePt material is one of the promising candidates for the future magnetic recording due to a high value of the magnetic anisotropy, assuring long-time thermal stability . From this point of view, the possibility to switch this material by ultra-fast laser pulses is very important for future technological applications . Recent experiments using the linearly polarized pulses in FePt show the change of the magnetization dynamics from fast to slow recovery as the pulse intensity increases . It has been also recently reported that circular polarized lasers are capable to switch the magnetization in FePt . This talk will present the results on micromagnetic modelling of ultra-fast magnetisation dynamics in FePt thin films induced by both linear and circular polarized lasers .