Preparation Of FeCo-based High-frequency Soft Magnetic Films And Research On Microwave Soft Magnetic Properties

Electronic components of Integrated circuits?IC?are developing towards high integration,miniaturization,and high frequency with the progress of information era.The working frequency of magnetic IC components is limited by the ferromagnetic resonance?FMR?frequency1)of soft magnetic films?SMFs?.Therefore,it is long-term desired for the SMFs with high1)and high permeability to improve the microwave performances of magnetic IC components.FeCo-based alloy films have been widely used in high-frequency soft magnetic IC components due to their excellent soft magnetic performances,such as high saturation magnetization 4?M_S,high permeability?,and low damping constant?.In this dissertation,we emphasize on the improvement of the uniaxial anisotropy field and the FMR frequency of the FeCo-based soft magnetic thin films.The major research work is listed as follows:Firstly,we prepared?Fe0.7Co0.3?1-x-Bx?referred to as FeCoB?films with B composition gradient by use of composition gradient sputtering method.In this study,the effect of sputtering pressure on microwave properties of FeCoB thin films was explored.Moreover,a rotatable anisotropy in FeCoB SMFs is available,in which both the strength and the orientation of the anisotropy field₆)can be manipulated.As a result,₆)and1)of FeCoB SMFs increase from 86 Oe to 142 Oe and from 3.55 GHz to 4.82 GHz with the decrease of sputtering pressure from 0.5 Pa to 0.2 Pa,respectively.Secondly,we designed ultrathin Ru-separated FeCoB/Ru/FeCoB sandwich films.It is uncommon that the optical mode FMR is enhanced in this magnetic anisotropy trilayers.As a control,we first prepared a FeCoB single layer with 50 nm in thickness.It is revealed that the1)increases from 4.23 GHz to 5.89 GHz with the increase of B doping.However,when an ultrathin Ru spacer is inserted to the very middle of the 50 nm FeCoB single layer,the FMR frequency is very sensitive to the Ru thickness.For sample with the Ru thickness of 3?,the1)dramatically increases to 8.36 GHz,which can be attributed to optical mode resonance with the antiferromagnetic coupling in trilayer.At last,a series of Fe56Co24B20 amorphous thin films with 65 nm in thickness were prepared by pulsed laser deposition with a tensile stress exerting on the single crystal Si substrates.As a result,stress-controllable microwave ferromagnetic properties with1)up to 4.03 GHz and₆)over 178 Oe were obtained by simply adjusting the magnitude of strain.