Fig. 3
(a) Illustration of the observed magnetization dynamics: (i) For t<0, the net canted magnetization \(\overrightarrow{M}\), \(\theta _c\). \(\overrightarrow{M}\) points in the equilibrium direction (grey dotted line). (ii) At t>0, \(\overrightarrow{M}\) magnitude reduces, and (iii) a new equilibrium orientation,\(\theta _c\) \(^{\prime }\), due to altered exchange coupling, results in increased in-plane projection. A red dashed line projection shows the increase. The competition between processes (ii) and (iii) results in ultrafast demagnetization followed by an increase of the in-plane component of the magnetization vector. (iv) For t>1ps, the heat begins to dissipate, leading to the restoration of the magnitude of \(\overrightarrow{M}\). (b) Illustration of the magnetization dynamics: static MOKE curve is quenched at t>0 (black to pecah color). Since at this point, the coupling strength is affected and considering the laser penetration depth, FeNi/FePt recovers by following the hysteresis of FeNi with higher MOKE rotation (green color) and later recovers to its original state on the longer timescale of ps.
