  The continuous reduction of magnetic units to ultra small length scales
inspires efforts to look for a suitable means of controlling magnetic states.
In this study we show two surface charge alteration techniques for tuning the
interlayer exchange coupling (IEC) of ferromagnetic layers separated by
paramagnetic spacers. Our study reveals that already a modest amount of extra
charge can switch the mutual alignment of the magnetization from
anti-ferromagnetic to ferromagnetic or vice verse. We also propose adsorption
of alkali metals as an alternative way of varying the electronic and chemical
properties of magnetic surfaces. Clear evidence is found that the interlayer
magnetic order can be reversed by adsorbing alkali metals on the magnetic
layer. Moreover, alkali metal overlayers strongly enhance the perpendicular
magnetic anisotropy in FePt thin films. These findings combined with atomistic
spin model calculations suggest that electronic or ionic way of surface
charging can have a crucial role for magnetic hardening and spin state control.
