Origin of perpendicular magnetic anisotropy in ultra-thin metal films studied by in-situ neutron reflectometry

Abstract: Perpendicular magnetic anisotropy (PMA) plays an important role in different spintronic devices. The rapid development of spintronics requires a better understanding of the nature and mechanisms of the PMA formation. In our article, we demonstrate the potential of studying PMA by in-situ polarized neutron reflectometry combined with pulsed laser deposition. Using these techniques, we show the formation of out-of-plane anisotropy in thin CoFeB films (1.8 nm) with a capping Mo layer. Investigating thick (5.3 nm}) and thin (0.5 nm) molybdenum films, we demonstrate that in both cases, PMA was established in bilayer structures without any thermal annealing. Also, we demonstrate how an additional silicon layer grown over the CoFeB/Mo bilayer can critically alter the magnetic properties of the sample. Such studies are possible only through the unique combination of the growth method with the in-situ polarized neutron reflectometry measurement technique. We believe that this approach will open up broad opportunities for the development and investigation of new spintronic devices.