Element Selectivity Ultrafast Demagnetization Dynamics of hybrid Stoner-Heissenberg magnetic alloys*

Laser induced ultra-fast magnetization dynamics (LIUMD) has been demonstrated to be an excellent way to manipulate the spin and orbital moments of magnetic elements onfemtosecond time scales.  Manipulation of the demagnetization amplitude and the corresponding time scale in an element specific way, for multi-component systems, is of fundamental interest to further engineer the LIUMD technique. The method holds promise to significantly change the future of spintronics and information technology in general. However, the interplay between various degrees of freedom in LIUMD of magnetic alloys is intricate due to the competition between different mechanisms and processes.  Wedemonstrate the role of spin-orbit coupling (SOC) on the demagnetization of Pd and theinfluence of the optical inter-site spin transfer (OISTR) mechanism of FePd₃, and provide via a microscopic picture of LIUMD in this system. Its  element resolved magnetization dynamics  is obtained by applying the state-of-the-art  time-dependent density functional theory (TDDFT). We have also found optical routes in which Fe to demagnetizes before or after Pd in FePd₃ providing the  fastest way to selectively engineer the demagnetization dynamics in alloys that is desirable for the spintronics technology.