Improvement of microwave magnetic properties by inserting nonmagnetic layer

Co/NM (nonmagnetic Ag and SiO2)/Co sandwich structure films with different thicknesses of NM were fabricated on Si(111) substrate via oblique radio frequency sputtering. With increasing thickness of nonmagnetic Ag [Formula: see text], in-plane magnetic anisotropy field [Formula: see text] initially increased from 100 Oe of [Formula: see text] nm to 220 Oe of [Formula: see text] nm, and then decreased when [Formula: see text] nm. Resonance frequency showed the same tendency with maximum 5.2 GHz when [Formula: see text] nm. Damp factor increased from 0.02 for [Formula: see text] for [Formula: see text] nm. The same result was observed in inserting oxide nonmagnetic SiO2 layer. This can be attributed to the competition between interface energy and exchange coupling energy.